A bit of a long one, so I'll try to keep some of these shorter.

Mamoswine -> A+
Fantastic breaker, with honestly a pretty wide range of at least usable items, completely unresisted stabs aside from very niche counterpicks, and the a resistance/neutrality to both fire and ice moves, allowing even more switch in opportunities. Has it's weaknesses, but overall a very well rounded Mon that does good into pretty much everything.

Lucario- C -> B- / C+
Lucario honestly does better as a mixed attacker then a physical one right now. I think that while LORB Extreme Speed on an SD set seems good on paper, in practice it's hard to actually get the set working how you want it to, like I'll be honest if I want a lategame cleaner that out speeds most things in the metagame with a good stab spammable stab combo then I'm just picking gapdos. But, all in all, +2 Tera Normal LORB kills like most things in the tier that don't outright resist or are immune to Lucario's stabs. The big issue then is preserving Lucario and not letting em be knocked a single time, but that's doable. However, I feel like a mixed set like
Lucario @ Shuca Berry
Ability: Inner Focus
Tera Type: Ghost
EVs: 80 Atk / 236 SpA / 192 Spe
Naive Nature
- Close Combat
- Flash Cannon
- Shadow Ball
- Nasty Plot
could be pretty good, you've got your stabs, and shadow Ball to kill the ghosts and particularly basc-F who can switch into your CCs. I chose this specifically since the idea behind this set was to kill Mamoswine in a pinch and demolish most other things in the tier. I didn't wanna go ALL in on special attack since at that point you get walked by SpD Hoodra, so CC it was, and you can boost up and force a tera on mons like Fez since Nasty Plot makes all your moves deal some pretty solid damage.
https://replay.pokemonshowdown.com/gen9ru-2275275044
https://replay.pokemonshowdown.com/gen9ru-2276721407 Vs. Feliburn, where I lose due to not calcing Lucario CC into Waterfall (which wouldn't have killed I later discovered), but the set generally does pretty well into the rest of his team, almost being able to kill the Gyarados but sadly due to my choke it was unable to. Note the fact it lived +1 EQ from gyara, does the same with unboosted mamoswine EQ too
https://replay.pokemonshowdown.com/gen9ru-2277716246-fdboh6rqsewjxw4o4bwy5pe485npx7kpw Lucario demolishes the opposing team, barely missing the rhyp OHKO with flash cannon, and showing another good MU into Armarogue, in which you're able to just kill em and click buttons
(+2 236 SpA Lucario Flash Cannon vs. 252 HP / 196 SpD Solid Rock Rhyperior: 432-508 (99.5 - 117%) -- 93.8% chance to OHKO)
TLDR, I think that Lucario is VERY unrated right now and can serve as a pretty good offensive breaker in the meta rn, with a great stab combo, pretty good typing, and the ability to run a plethora of options to cover its weaknesses
Ditto- C+ -> B-
Not much to say here, Ditto has been picking up lately and I'd say that while I would prefer it to be a C++ Mon instead of a B- which visually looks way too high, I'd say that ditto is just kinda good as an anti-HO Mon and an anti-sweeper Mon too, and while it fits primarily on Ditto-Stall teams (as the centerpiece guy), I would think he could also fit on like very passive BO or balance teams, and maybe even HO teams to be able to have some counterplay vs. opposing HO teams. Just theorymonning though, still a very weird Mon that realistically is staying at C+ due to general nicheness and lack of tourny reps.
Gallade- B- -> B
Genuinely a goated slow-ish breaker, like with a single boost this guy is taking names, souls, and bank accounts in broad daylight, it's absolute highway robbery what this guy can get away with. I get that now 80 speed is suddenly like the thing to beat with Mamo dropping, and you do run the risk of getting murdered by Mamo, but you do have some genuinely insane calcs you can get, and with one of your stabs not even making contact with talon you have less of a risk of getting burned, this guy should be WAY higher, even if the speed thing is an issue at times. I'd go out on a limb and say that this guy is like super good vs. slower, more passive teams and should be considered for more playstyle and teams and shouldn't just be locked into the HO webs teams that people usually default Gallade to. Could this be Gallades future? Honestly not sure, but I feel like it's way better then the other guys in B-.

Palossand- B- -> C+/C
With the expansion of hazard removal from being purely Cyclizar, his importance and niche has been diminished, like you still spinblock well, and that niche is functionally the same but with Mamo dropping, Volcanion doing better, and Noivern, Geezing, and Talonflames's rises in popularity, it just doesn't have what it used to have. Still able to be a fat wall, but with way more ways for teams to take it out/invalidate it.

Espeon- B- -> C+
Espeon just kinda... Isn't that good? Like it's got a real valuable niche on weather teams for acting as your "hazard control", especially on snow teams with eject button sets... but other then that, with no real spammable stabs and no access to fast boosting options, you're kinda just outclassed by other CM sweepers, and outdamaged by faster mons of similar speed tiers.

Slowbro-Galar- B+ -> B
I'd say that Glowbro still is good in specific situations, specifically stall teams as a regen Mon with toxic, but overall is threatened by a lot of the meta, especially Mamo. Regardless an interesting sidegrade to Slowbro that isn't completely up the creek.

Porygon-Z- B -> B+
A pretty good HO Mon that I'd say has real potential to be considered on both HO teams and regular teams. Download lets you achieve absurd numbers, and agility lets you outspeed a crazy amount of mons, even gapdos.
ALSO
please for the love of god use expert belt, hdb is not that good.
With Expert Belt you can OHKO cyclizar with +1 Ice Beam, gives you a 25% chance to OHKO Necrozma with Shadow Ball, and generally lets you nuke anything you have coverage for.
+1 252+ SpA Expert Belt Porygon-Z Shadow Ball vs. 0 HP / 0 SpD Prism Armor Necrozma: 293-346 (87.4 - 103.2%) -- 25% chance to OHKO
+1 252+ SpA Expert Belt Porygon-Z Ice Beam vs. 104 HP / 152 SpD Assault Vest Cyclizar: 307-362 (100 - 117.9%) -- guaranteed OHKO
+1 252+ SpA Expert Belt Tera Ground Porygon-Z Tera Blast (80 BP) vs. 120 HP / 56+ SpD Goodra-Hisui: 324-384 (97.8 - 116%) -- 93.8% chance to OHKO
+1 252+ SpA Expert Belt Tera Ground Porygon-Z Ice Beam vs. 0 HP / 4 SpD Zapdos-Galar: 434-511 (135.2 - 159.1%) -- guaranteed OHKO
(they don't even OHKO you with CC or brave bird so you could just gamble and set up agility anyways on Gapdos)
252 Atk Zapdos-Galar Brave Bird vs. 0 HP / 0 Def Tera Ground Porygon-Z: 255-301 (81.9 - 96.7%) -- guaranteed 2HKO
252+ SpA Expert Belt Tera Ground Porygon-Z Ice Beam vs. 0 HP / 4 SpD Zapdos-Galar: 290-343 (90.3 - 106.8%) -- 43.8% chance to OHKO
Porygon-Z @ Expert Belt
Ability: Download
Tera Type: Ground
EVs: 252 SpA / 4 SpD / 252 Spe
Modest Nature
- Agility
- Tera Blast
- Ice Beam
- Shadow Ball
just use this and kill everyone
like you have to think a negligible amount on who to come in on, but you can just turn off your brain and win games it's dummy simple. HDB only matters for non HO teams, and even then with good positioning and the proper gamestate you really don't need to come in more than once, cause that one time you come in you win. Use expert belt and all your dreams will come true

Slowbro- S -> A+
Not really as good as Gapdos is my reasoning. Still a great mon, with both the future sight thunder wave set and CM set both being great, but just not as good rn. Amazing physical wall, just under a lotta pressure and not up to the same stuff as Gapdos.

Talonflame- B+ -> B+
I'd argue against LBN here, I still think a defogger with access to burn is good. It is able to find defog opportunities pretty well, and the ability to cripple setup sweepers and physical attackers is great, especially in conjunction with Quagsire, like I think these two pair amazingly. You can burn say, a Terrakion on an SD, and switch out safely into Quag. It's honestly not complete dogshit like how he would have you believe, and I think that it's ability to mitigate damage for its team and punish random physical attackers is great. Unlike how LBN would have you believe, Noivern and Talon actually don't overlap as harshly as you'd expect and they occupy very different defogger spaces in my mind, with Talonflame being the more defensive and safer vs. Bisharp pick, and Noivern for the more offensive teams for when you also need to pack on a Volc counter. (also noivern also doesn't check Mamo why are you offering it like it can, at least talon can burn mamo)

Hippowdon- A -> A+
Absolutely murders the physical attackers of the tier, and has plenty of amazing matchups into the various top dogs of RU (except for the actual dogs of RU, Entei, Suicune, Raikou, the bunch.). Sandstorm helps out with passive damage into HO teams, so even while you're being hammered and staying passive you're still doing damage, NOT TO MENTION that it breaks focus sashes and blows past Armarogue Endure, so you can play more offensively into HO with Hippo, you have a great (if kinda luck reliant) MU into Bisharp, with stone edge/Rock slide being able to cover most defensive teras, loads of longevity, and the ability to take 36% from Gapdos on a BB switch-in. Genuine GOAT of a mon. Amazing into most leads too, and tera can make em stick around even longer (additional points for not being tera reliant at all times)

Terrakion- A- -> B+
Still a good HO lead, but bros kinda fallen off ngl. Cool that he's a fast offensive rocker with good stab combo and coverage but like what does he do, I genuinely haven't seen a convincing argument or showcase of the guy in like forever

Reuniclus- A- -> B+
Fallen off CM sweeper, HOWEVER there might be remaining tech in AV sets, so it might not be fully over. Might be partially over though.
Outclassed by Suicune and Slowbro, with very limited coverage, but at the very least good abilities.

Breloom- B- -> B
Ditto what LBN said, very cool Mon with the extremely unique Poison Heal ability which lets it absolutely DEMOLISH bulky / passive teams with a leechtect set. Very nice, very cool.
https://replay.pokemonshowdown.com/gen9ru-2272709561-gnil483kxdq5pmyx7pm8xv4hbw7qa4mpw?p2
Breloom essentially 6-0's a (very suboptimal) stall team thanks to Toxic Orb + Leech Seed leading to an insane amount of healing for just one Mon, allowing you to essentially ignore hazards and passive damage, the two things stall needs to win.

Bellibolt- B- -> B
I'd say Bellibolt sadly isn't entirely there yet, but the main set I propose people try out is this...
Bellibolt @ Rocky Helmet
Ability: Static
Tera Type: Ghost
EVs: 252 HP / 252 Def / 4 SpD
Bold Nature
IVs: 0 Atk
- Discharge
- Slack Off
- Muddy Water
- Toxic
For one, you have the option to essentially cheese your way outta any bad physical attacker MU, but on the other hand you also can very easily just sit on a lotta stuff, like you are still just Bellibolt, and cause of that you can very easily play for time, toxic switch-ins, and spam muddy water if you don't know what else to do to play for a miss and para-centric wincon.
The main thing this set counters is Gapdos, which is why I would like to see this guy higher up. If Palossand could get B+ before just for walling Cyclizar well and spinblocking, I'd say that Bellibolt with it's ability to cripple Gapdos, and naturally resist one of Gapdos's stronger stab options also deserves to be near that same echelon.

Forretress- D -> C-
Pretty much what Feliburn said above.
Forretress in my eyes is better used less as a jack-of-all-trades where you try to put as much on as possible, but better used as a hazard removal options with a lotta free moveslots. You don't really want to put EVERYTHING on this guy, as that just gets you a mon that's mid at everything, but instead you probably just wanna play towards it's strengths as a physically bulky rapid spinner that isn't avalugg. Like, that in an of itself is its niche. It's got every hazard and pivoting, so all you need is rapid spin, body press, pain split (so you can actually stick around) and like either volt switch or a hazard, that right there gives you all you need. You do have options with replacing pain split with like maybe t-wave, but overall I'd say that forre, along with solid usage by respected top players and the stuff said here and above, definitely deserves to be unbanned from the discussion lock and moved to the next closest spot of C-.
Also I want to say that I think that the PMD sprite or, at the moment, the regular SM sprites are fine. I think it's actually ok if we have fun with our VR, and that even if one specific guy doesn't like it, it should be kept as it not only gives our VR an identity, it also just looks fun. I did it with Gallade and Ditto, and it's not really the end of the world if sprites are used to represent mons, nor is it a crime to have little jokes with them, either.
anyways like and subscribe to the RU YouTube channel for no other reason than they cool