I'll give thoughts on stuff I've either used/built with or faced a lot and a couple things that I wouldn't have talked about if they weren't nommed in the thread (not gonna comment on stuff like Mewtwo because that's still in development - please don't theorymon with it that's not how this works).

Up to A+/S: I see this as similar to Melmetal's original ranking in that it's perfect defensively for the current meta and a staple on most good teams. Every time something that isn't Fish/Beak/V-create gets banned this just gets stronger and more logical to build with. Unlike most walls it is almost entirely consistent at its job, you're not really getting lured by anything you beat other than the Intrepid Sword guys with Photon (yes you should be running this but it is still incredibly uncommon and hard to improof regardless). It's worth noting that this mon is kind of a chip magnet in general, a lot of what it wants to beat runs Knock/Wisp/Hazards so it is possible to end up behind the flow of the game if something goes wrong. With the offensive sets I think they're definitely a bit overrated, the mon is bulky and that's cool but without one of the first two defensive abilities i mentioned you're still throwing away quite a bit of utility. After trying the Sheer Force hazards set and playing against it a bit I kinda came to the realisation that its free offensive turns aren't particularly free, you just can't afford to get Knocked for many reasons and the general lack of OHKO power leads to various situations where you're engaging in chip trades you don't want to be in. Quiver knocks up the threat level a ton and cuts away a bunch of soft checks and I'd recommend that over hazards or Recover if you are going to run offensive Etern, just be wary that Ice Scales may halt your offensive progress which is annoying for any set that doesn't pack an in-built way to cripple its checks.

Down to A+: There's not much to say here, we have other equally good ways to build that don't revolve around this mon now. It's still v good and doesn't have huge drawbacks but once you start trying to maximize its potential as a wall you become semi-passive in that you hit specific mons hard but still get taken advantage of by others for somewhat free momentum. Similar to Etern a lot of sets look to punish the super fat walls in ways other than hitting them with damaging attacks and Melmetal suffers from that as well. Bounce used to be insane, it's still good to have a bouncer but the rise of more convenient Knock absorbers (mainly the PH mons again) prevents most of the cases where a set like that on Melmetal used to win long-term.

Down to A: Multi-attack sets are pretty dead rn, honestly I think the main issue with them is just that they don't really fit in with the support you can afford to give them in this meta. You have Choiced breakers forcing immediate responses from inconsistent defensive mons and you have other stuff (mainly Poison Heal) aiming to control the game via residual damage and keeping momentum. Smash Zekrom doesn't really fit in with either crowd because it's too slow and weak initially to control the game, but when it comes to breaking you usually have to hit the Smash button first which can be played around. PH makes much more sense because it becomes much easier to click the setup move and cripple your checks, which means you get a consistent output from the mon. The problem with PH isn't so much that Grounds check it as much as it is that things other than Grounds check it. If you were able to freely run Wisp + Knock with no consequences you'd be able to always burn Grounds and remove their items which would be enough for teammates to break through. If you throw in the fact that people are also running mons like Etern/PH Resh though then it's much harder to choose your set and teammates. It's still very much a redeemable mon, people don't seem to be mentioning positives when talking about this but the non-Ground non-Etern checks can often be given a run for their money over the space of a few switchins, see
this replay as an example of how that can play out.

??????????: This mon's weird. I think it's kind of a death trap if you're trying to build normally with it, I see a lot of structures which are effectively balance teams with DGZ as the breaker and these risk falling flat on matchup in a lot of situations, especially in the case of Band. Having to account for Rocks, fitting the correct coverage, playing around Dynamax, and most importantly the random PH mons which are bound to come in on half the team and win more efficiently than Darm or just stop it from breaking (looking at you Zama). I'll elaborate on this more in some of my other noms but the general idea is the CB DGZ balances that were running over the meta a couple months ago are constantly becoming more and more inconsistent. The thing is, this is still the most dangerous mon in the meta imo - it has the highest potential to get a ton of work done in a short amount of time (though it often gets less time to work with compared to other top offensive mons). This opens up the possibility for different ways of building with it to shine, the two I've been seeing lately are DGZ spam and simply switching the CB sets for something more flexible like LO Magic Guard (see
Loser's RMT). Both of these aim to cut some of Darm's weaknesses while still focusing on Darm's main niche which is having 0 switchins - MG LO gets rid of the Choice Lock and general weakness to being chipped, whereas Darm spam serves as a way to ignore some of the building limitations that would normally come with a Darm balance team, trading the ability to cover threats and even to improof for a faster playstyle that also attempts to cut down on Darm's need to find free switchins from its teammates. Stuff like Darm spam is obviously high risk high reward but it's new and confusing enough for me to shy away from judging Darm's viability as a whole, and I'm not sure anyone else can give a better account here so I've left it as ?????? because ??????.

Down to A-: This just isn't that good tbh, the dynamics that made Imposter so good last gen are mostly missing right now. When it's not running Scarf it can heal up on some defensive mons, except it barely matters whether Imposter is healthy because it just gets slammed by most of the offensive threats anyway. Scarf is alright, some people are very tight with improofs when it comes to stuff like Isword, so at least you can punish them. Also if there's anything you want to scout in this meta it's Darm and other things that also slam you for a ton of damage so yea it's kinda difficult to use this rn compared to the other stuff in A rank where you have more control over their output.
Oh god I just realised I'm about to murder A- rank where are they all going LOL.

Down to like B at least tbh: This has been beaten to death by now I'm pretty sure everyone knows this is out of place by now.

Up to A/A+: This has been covered a lot and I think it's fairly self-explanatory, this is the third of three "good" defensive mons in the meta and it should rise to reflect this.

Stay in A-: Yeah you definitely have to prepare pretty speciifcally for this but with Zama-C back I think we have a very good counter and a good amount of checks which I generally find is enough to annoy Kyu-W heavily. Outside of that it has some utility but is still fairly slow with not the best typing.

Maybe rise to A? I'm not fully sure about this because we can't compare it to stuff like Kyu-B when that's not really an A- mon, but it feels like every time I see Zamazenta it's at least neutral in the matchup, and sometimes it just doesn't die. A lot of the more offensive builds really struggle against Cotton Guard, and most builds in general just kinda struggle to put pressure on PH when considering moves like Knock and Wisp. It's a p easy mon to get in and much harder to take advantage of, considering you're beating some of the more common breakers like Darm 1v1 a lot of teams kinda try to sit there wondering how they're gonna make any progress against it which is favourable for the Zama user as they get to control the game. Intrepid Sword is hot too, definitely one of my favourite choiced breakers even though I'm generally not a fan of them, avoiding death by Dynamaxed Imposter is a big plus and the Speed tier makes it pretty easy to just throw off whatever attacks you feel like using, including U-turn because Zama fits that much more easily than most choiced guys. You lose out on a few switchin opportunities compared to PH though.

Drop to B+: This is dangerous, but definitely kinda hard to run due to various mid-grounding options and lack of bulk. The rise in defensive Etern p much makes this drop a subrank on its own tbh.
Somehow B+ manages to just be irrelevant in the current meta compared to many things lower than it idk how that happened. Kill Solgaleo and Zacian, Pex needs to drop too it doesn't keep up with the meta.
Ferrothorn should drop a little bit too, I don't fully agree with the "what does this do" comments though. Primsea in itself is already such a valuable ability with its weather resetting, the difference between this and Melm is that here we can at least check Reshiram and it's one of the harder answers for it to cheese through. The better question is what it does over Zama-C, and that's not really about walling FishBeak, because you just don't. The difference is that getting 2HKOed by Banded Fishious Rends when trying to reset weather/block darm V-create instead of getting OHKOed is pretty major for those types of matchups. Ferro would fit fine in B imo.
I think people are overestimating the cost of running less efficient defensive mons on teams, there's a lot of auxiliary roles that are really cool to have on teams when prepping for various styles, and even if you don't have the ability to customize a less good mon to beat a wide range of threats, you can still make it useful in actual games. So many of the cheese teams in this meta struggle to operate if
anything clicks SR, it doesn't have to be an efficient SR setter against all types of teams to put in work, you're just targeting the teams like rain that rely on pivoting so much that the Defogger is running a set like Spectral/Teleport/Fog/Recovery (awful at removing hazards from anything). Pivoting moves can be the same in a lot of cases, running them on the good defensive mons can take away from their effectiveness, but having even one slow-ish pivot on your team is very useful. Another example would be Prankster users - so many mons can pull off Encore + Haze Prank sets at roughly the same effectiveness, it just comes down to your team's needs. Gen 8 teambuilding is not as streamlined as Gen 7 teambuilding, nearly everyone's building balance/BO and they know they will want/need to delve into the pool of "ass" mons to fit the roles that the teams need in order to function well. There's some really clear cases of some of these mons just being too outclassed and then some which aren't outclassed and actually see a lot of use. Meanwhile offense in this meta is mostly carried by Species Spam and don't have as much ability to gain a niche just based on their typing for example, so niche offensive mons have it a lot worse when it comes to justifying their use. I don't feel like the current VR or the nominations reflect this very well:

Stay in B-: No one's really using this right now and it's far from an easy slot (outside of being a PH user), I don't see why this needs to rise.

Up to B: Everyone's nomming this to B- but idt there's any need to keep this so low. It provides more than our B- and C mons anyway, it may be flawed but even acting as a check to Zac-C and Zek and complicating Darm's life when it comes to choosing sets is a good start, Ground STAB is also good enough that you can free up the team utility slots that i mentioned before, Teleport works really nicely on this mon especially.

Up to B: Similarly useful but somewhat flawed mon. Has multiple respectable sets that can justify their place on teams, as just one example Resh doesn't burn PH Lax, this is majorly useful as it changes the whole dynamic there and avoids having to throw Darm and Resh under the same blanket which is somehow too small for either of them.

Up to C: Having used Ice Scales Incin more on a few teams I am happy to call it easily more worthy of a teamslot than p much the whole D rank, this feels awkward at times but for the most part it takes pressure off the team by Spinning and throwing out Knock Offs, obviously boots help there and you take care of some important mons with limited checks, namely Kyu-W and Lunala. Its main weakness comes down to whether the rest of the team can keep up with the game when Kyu-W and Lunala click Volt Switch, but that's just kinda what makes those breakers good because you can't counteract that possibility anyway. The other thing is it's v similar to Scales Zama-C in terms of what it checks, the difference here is you can check Resh better which is enough to give it a niche.

Up to C: Look this mon isn't great and Ice Scales faces competition with Scales Lax which is also meh, but it has the right typing to pull off Prank and do something without being outclassed, and I mean... look at D rank.

Stay in B-: Specs Adapt Pult + Spikes = profit. This at least has a niche over Lunala because you have more speed to make use of your broken Ghost move and STAB Dmax Cannon which is really helpful for the lategame. The speed tier and spammable STABs, as well as the ability to fit Volt Switch on its set, give it enough justification to be used on Spikes builds, without Spikes you miss a few big KOs but you can at least buy time/momentum.

Up to B+: Specifically based on the PH set. This is one of the mons where I keep watching it put in work in actual games even though it looks meh in the builder. One of the easiest mons to scout defensive mons and pivot out with, Protect clones are v annoying for the pivot + choiced breaker teams as a result (including rain). Right now my favourite Tect clone is King's Shield on this, the attack drop can really help vs things like Darm, but you do lose out on blocking Wisp and Defog and it's harder to activate the Toxic Orb early game. Also there's generally not much Bounce in the meta so you're getting free hazards a lot of the time.
One last thing because everyone seemingly forgot to do this.

Up to not UR (probably C)
Rain has had a bit of a surge as a fringe playstyle and it kinda relies on having both Keldeo and Barraskewda to be a threat. Keldeo's important here because you need to have a Special breaker on the team that can force out some staples and make progress if the opponent doesn't have a bulky Ice Scales mon. In any case once you shuffle the opposing team you can actually start to do work with the likes of Barra, otherwise you just get situations where your best way to kill FC Melm or something like that is to pivot into Barra and try to beat it 1v1 which is a horrible idea.
Wew this was longer than I expected but so much has changed since this was made, hope we see an update soon.