New meta, old favorites:

A+ -> S
Slowbro is and has always been the best mon in the tier. Defensively, its bulk, typing, and ability lets it check a plethora of important threats time and time again. Offensively, it can spread status with scald and thunder wave, function as a win condition with calm mind, or force progress by setting up future sight for its partners. Furthermore, thanks to regen recovery it is not as easily forced to recover as other mons, which has the dual benefit of enabling its user to play it more proactively than other defensive mons while also not being anywhere near as prone to getting PP stalled out of recover PP in longer games. Due to these qualities, Slowbro is the most splashable mon in the tier. You could fit it on almost any given team, and at almost any given point in the building process, with the exception of HO. Moreover, it performs consistently in any given match up. There just isn't such a thing as a bad match up with Slowbro. It is always useful. I can't fathom what more anyone would want out of an S-rank mon.

A -> A+
I love using Mamo. It has two immensely valuable properties. First, it can break anything with the combination of eq/crash/knock (doing so is especially easy in conjunction with future sight Bro). Second, its priority is a lifesaver into set-up mons. I can't count the amount of times where it has saved me versus a weakened Bish, Arma, Gyara, Hilligant, Maus, Mimi, Entei, Lycan, or what have you. It also helps that it provides a volt immune, and that it has a decent speed tier and alright natural bulk, as this grants it many more opportunities to break than, say, a Crawdaunt, but this is more of an added benefit than a primary reason for using it imo.

A -> A+
Another personal fav of mine. Its bulk enables it to trade and check all sorts of stuff, while it makes progress offensively by clicking Draco and Knocking all the good Draco resists (Rachi, Regi, Empo). I'm especially fond of draco/knock/protect - again this has wonderful synergy with future sight Bro - since protect grants it the option of scouting out choiced moves and gaining lefties recovery. Take your pick regarding fourth move - tbolt (empo/cune/bro), eq (empo/zone), heavy slam (umb, garde, mimi, bee), and acid spray (draco kos practically all non-resists at -2) are all good on their own terms - but just draco and knock alone is oftentimes sufficient.

A+ -> A
I don't like Noivern as much as the A+ mons. Specs is good but prediction reliant and weak to sr. Defog loses to most rockers 1v1 and needs to be wary of clicking it into Gap/Empo (granted, it's risky to hard Gap on Vern and you could build your team such that it has answers for +2 Empo). Offensive pivot sets feel alright to me but not amazing. It is certainly valuable to be faster than all non-scarfers, and having STAB Draco and U-turn will always be valuable, but I don't value it as highly as a Volc, Bish, Mamo, or Goodra.
A -> A+
I agree, Geezing leaving makes all its offensive sets better. No point in regurgitating the same arguments outlined above, but I would add that it's a great partner for future sigth Bro.
A- -> A
I don't think this mon should have dropped to A- to begin with. I've always been fond off Hippo balance. But I don't agree that Geezing rising makes any difference for it. Mons like Flygon, Pads Gap, Azelf, Noivern are more annoying for it than Geezing imo since they wall mono quake hippo
and threaten to make progress, whereas Geezing just sat there. You could always hard from your Hippo to Bro or whatever and be fine versus Geezing. Moreover, if you have a future sight set by Bro, Hippo can actually force progress either with edgequake or by phazing the opponent out as they hard into, say, their own Bro to absorb future sight + eq. Finally, Geezing was a neat partner to have alongside Hippo, so I don't think it leaving affects Hippo all too much.
B- -> B+/A-
Speaking of Flygon, this mon has always been underrated imo - special and mixed sets were underexplored and good in the Geezing meta - but now it should be obvious that the rank it has is too low. With Geezing and Mence leaving, DD Flygon got a major upgrade, in that it no longer needs to run DD Tera Blast Steel for Geezing and that it lost a major source of competition in DD Mence. I would expect DD Scale Shot sets, in particular, to see more usage.
B -> B+
Benefits from both Geezing and Mence leaving. Cute option.
B -> B+
Muk is great. You just sit there and spam knock rest talk haze, walling all sorts of stuff while removing items and spreading items. I've seen some mentions of protect Muk on discord but I have not found myself in a position where I have had the luxury of using it since it generally needs rest to absorb scalds and sit on mons like Bro and Cune. Anyway, it's a defensive mon which can check a bunch of special attackers, function as a status absorber,
and make progress by brainlessly clicking poison touch knock. Would highly recommend using it together with future sight Bro, in particular (notice how everything synergizes with future sight bro btw).
C -> B
Let's raise this mon in the VR. Dumping it into UR doesn't make sense. Offensively, it's decent at making progress with gunk, cc, and sd, whereas sucker is valuable to revenge set up stuff or to clean after an sd (provided things have been sufficiently weakened). Defensively, its ability enables it to function as a vincune counter and beam cune check, and it fully walls CM Bro if tera dark. I've found myself building lots of HO and BO teams with this mon, usually with balloon as the item. Try it, it's cool!
-> C
I would only consider using either of these on stall and I don't consider stall to be particularly good (although it is viable). Accordingly, I see no reason for either of these to be in the B ranks. I think it's reasonable to prefer Blissey over Chansey given that HDB is a useful tool for preventing chip but I also think the additional bulk on Chansey is sufficient to give it a niche. Staving off Armarouge is quite important imo and it can trade 1v1 vs a surprising amount of physical attackers, especially post-tera, if need be. The difference in bulk is noticable into mons like Gapdos, Mamo, Lycan, Crawdaunt, Gatr, Azelf/Mew (psyshock), and DD Necrozma, to name a few. You obviously don't want to use Chansey to trade versus these mons unless you're forced to, nor do you want to use the tera unless it's absolutely necessary, but I think it's useful to have the opportunitity to do so.
UR -> C
Diancie is cool, especially into HO. Offensive trick room with meteor beam is a pretty cool mon both for making progress and for cleaning in the end game. It's difficult to build around but in battle it tends to perform decently. Worthy of being ranked.
I don't have any thoughts on anything else atm. Obviously, what I care the most about is the high ranked mons, hence why I mentioned them first.