Mega Post of my thoughts on the current meta:
Delphox: A+ => A/A-
This mon does not benefit from current meta trends, its scarf set is setup bait for two very spooky mons in Houndoom and Incineroar, its easily trapped, and while its CM set is still good, that's honestly the only one of its sets really deserving of an A ranking. Additionally, Pursuit Rhydon is super scary for any non-CM set, as it trivially removes Delphox if it ever clicks anything but Grass Knot, while also annoying the hell out of the wish/tect set, which is notably easily pressured thanks to how much it is often expected to do and Stealth Rock. Not much to say other than that current meta trends have made some of its answers rather prominent, and its hurting as a result.
Klinklang: A+ => A
Not nearly as sure on this one, but Steelix is in a great place, Slowbro is in a great place, and many mons that soft check it such as Incineroar and Hariyama are present in the meta. Real iffy on this one, just mainly nomming based on gut feelings and the prevalence of certain answers. That and the fact that Venu, a mon its occasionally needed to check deals way too much with LO Leaf storm (50% min). Again, real iffy on this one.
Steelix: Agree with A => A+
Basically, Sneasel is as common as ever, its typing remains useful as ever, and it heavily annoys Maud, which has gotten more prominent as of late. Not too much really changed for this mon other than the discovery and popularization of alternative sets such as Curse, but its just generically good in the meta, and that does a ton for it.
Rhydon: A- => A
Ok, so this mon benefits heavily from a number of meta trends, being the only good rocker that can beat Incineroar 1v1 (+2 252+ Atk Incineroar Malicious Moonsault vs. 252 HP / 0 Def Eviolite Rhydon: 337-397 (81.4 - 95.8%) -- guaranteed 2HKO) even after rocks, though it needs to be at really high HP to do so, forces Houndoom to blow its Z-Move to bypass it (very possible to outpredict, and not even a guaranteed OHKO, can even ev to avoid), and with Pursuit, it can straight up remove stuff like Delphox, Choice Scarf Rotom, and providing excellent support for the rising star of NU, Venusaur.
Houndoom: Agree with B+ => A-
This is imo one of, if not the best Scarfers in the current meta, providing great utility with Pursuit and a last ditch Dbond, and good stab coverage with its well, stabs in Fire and Dark, letting it be one of the more reliable ways to revenge kill Celebrate Venusaur after its set up (252 SpA Houndoom Fire Blast vs. +1 0 HP / 0 SpD Venusaur: 216-254 (71.7 - 84.3%) -- guaranteed 2HKO, only needs a bit of chip). The prevalence of the scarf set has also majorly benefited the NP set, which can use that to bluff a scarf and get some set up. Note, I honestly think this rise should be due to how good its scarf set is, and how that benefits its other sets so much.
Incineroar: B+ => A
This mon has proven itself insane in recent play, having great bulk letting it be a useful utility check even when uninvested to a bunch of really scary stuff such as Venusaur, literally any fire type, or Sneasel, while Malicious Moonsault and Z-Flare Blitz provide it unmatched wallbreaking prowess, letting it put in insane work. It punishes essentially anything slower than it very heavily with its insane power and stab combo. Considering the meta is somewhat balance focused atm, this is a good thing. Basically, good defensive typing atm (provided you can control SR), matches up impeccably vs anything fat, and just high enough of a speed tier to outrun anything defensive makes it great.
Braviary: Agree with B+ => A-
Agree with what waters said above, its a great scarfer atm, and non-scarf sets threaten fat well, while matching up well vs Venusaur.
Piloswine: B+ => A-
This mon is one of the few Ice resistant rockers atm, which can be incredibly useful for role compression on many teams. Additionally, its stab coverage remains really annoying to face if you somehow aren't using a Slowbro, and reasonably strong priority on a rocker can be invaluable on many teams. Not too much has changed for it, just figure its ranking should reflect its place in the meta as a rocker with good offensive presence, which provides a very unique defensive niche.
Rotom: Agree with B+ => A-
Honestly, the main reason I believe this should move up is because it is honestly the best defogger in the current metagame with its Colbur Hex Defog set, which comes in essentially for free on Steelix, while punishing many potential switch ins with either a Volt Switch or a Willowisp. Yes, it is annoyed by the Fire/Darks rising up in prevalence, but being a defogger that comes in for free on the most common mon in the tier without sacrificing momentum is amazing atm.
Hariyama: B+ => A-/A
Read what I wrote above for my thoughts on the matter.
Zangoose: B+ => B
This mon is barely used for a reason: the costs of building around it are often greater than its rewards, as to use the Belly Drum set effectively, you need very effective Pursuit support, and you often are almost forced to run a Memento user to allow Zangoose to set up, which can be incredibly telegraphed. Additionally, and more damningly, Colbur Slowbro generally tanks a hit even after Belly drum, and does enough that if you even take 20% damage when setting up you die (0 SpA Slowbro Scald vs. 0 HP / 0 SpD Zangoose: 130-154 (45.2 - 53.6%) -- 90.2% chance to 2HKO after toxic damage). Basically, it ain't amazingly favored by meta trends, and while its alternative set, Toxic Orb breaker is very usable, I don't believe either set necessitates a B+ ranking.
Altaria: Agree with B+ => B/B-
Ok, so this mon is setup bait for legit like the entire tier, is a SR weak defogger, and while yes, its probably the easiest way to deal with Slowbro in the tier, it doesn't really do anything off of that, with both mons just sorta Toxicing eachother and setting there, with Alt being essentially unable to do anything off of that besides sit passively and Flamethrower/Toxic stuff, while also being setup bait for legit like everything threatening atm, see Incineroar.
Omastar: B => B+
Ok, hear me out; this mon turns many choice locked attackers into set up bait, threatens a lot of fatter teams thanks to nearly unparalleled power once set up, and thanks to Delphox plummeting out of omnipresence, its a lot more annoying to revenge kill. Thanks to Z-Moves, it can fairly reliably bypass many common water checks, (+2 252 SpA Omastar Breakneck Blitz (190 BP) vs. 252 HP / 4 SpD Slowbro: 454-535 (115.2 - 135.7%) -- guaranteed OHKO), and in general, Weak Armor means that even if you can't set up, you can still contribute very effectively vs more frail teams. Yes, it is weak to priority such as Mach Punch, but like, the main Mach Puncher in the tier, Hitmonlee is at record lows of usage, and Toxicroak, a mon that should answer it, is OHKO'd with a lucky roll after SR with Ice Beam (+2 252 SpA Omastar Ice Beam vs. 0 HP / 4 SpD Toxicroak: 254-299 (82.7 - 97.3%) -- 25% chance to OHKO after Stealth Rock), or just using your Z-Move on it, while it can't even do 50% with Sucker in return.
Vaporeon: B => B- (maybe lower)
Ok, so legit, what does this mon excel at atm, other than inviting in Venusaur, Toxicroak, and Heliolisk in for free? Sure it can Heal bell, but there's so much Toxic spam being thrown around atm that 8 PP often isn't enough, and the opportunity cost of letting in 3 of the Tier's most threatening breakers in for free is rarely worth it outside of very specific balance teams, which are often ok with having Slowbro. This and the fact that Vileplume also does the Aromatherapy thing while being Toxic immune and having broken move Strength Sap.
Don't really want to spend much time on C-ranks as they're huge, and this post is already getting long, but:
Golbat: C+ => B-/B
Ok, so this is the hardest counter to Venusaur in the tier, and legit you have to struggle to lose to Venu when using this mon if you have even acceptable hazard control. Sure its generally only an ok at best Defogger, but the Stallbreaker bat set with Taunt/Brave Bird/Toxic or Super Fang/Roost can put in great work vs a lot of fatter styles that are floating around currently, while nearly countering Venusaur and Toxicroak, which can be absurdly useful for many teams atm. Its insane bulk and great typing are just so useful atm that I struggle to justify ranking it in the C ranks.
Kabutops: C+ => B-
Ok, so if you ever hit Kabutops with a Knock Off it becomes faster than your entire team, and immediately threatens everything with the SD/Stone Edge/Waterfall/Aqua jet set, notably OHKOing Slowbro after rocks with a +2 Z-Edge. Yea, its worse than Omastar, but having priority is insanely useful at some times, letting you provide an emergency check to stuff like Houndoom, dealing 75% min, while Z-Stone Edge is strong enough to OHKO would be counter Toxicroak after a SD.
There are more changes I could suggest, but tired atm.