ftr i am by no means an expert pokemon player, but i'm getting back into current gen(because I personally was not a fan of gen 8) and wanted to share my thoughts on the metagame rn
On Terastilizing
I think Tera is probably still broken, but not in the way that I initially suspected it would be. I think Tera being able to pick your coverage with Tera blast is mediocre and a budget z-move in many scenarios. Not only is the resulting move actually not that strong but if you're picking a tera type for coverage it may also expose you to defensive weaknesses that can hurt a lot more than they help(e.g. a hypothetical tera-ground volcarona is now vulnerable to ice shard). However, the defensive aspect is actually the most broken aspect of Tera, because you can limit the capacity of your sweeper to be revenge killed. It's not exactly an offensive use of Tera but not one you'd see on defensive pokemon either; it's specifically scenarios where your offensive mon is threatening your opponent bar a certain priority move/fast mon that if you pre-empted you could totally just ignore and continue breaking/cleaning/sweeping. I've only really seen this in any regularity with roaring moon but the fact that any offensive pokemon can and will just cheese you by picking the right tera type is immensely frustrating to me and is probably my least favorite aspect of this mechanic.
I genuinely think we should give the mechanic at least more than a few days, though. I think there are more glaring problems(e.g. Flutter Mane, Booster Energy) that feel even more broken to me right now, and there's definitely some vain hope in me that this mechanic balances itself somehow, even if I'm pretty sure it'll only get worse as it gets optimized over time.
Where are my Ground resists
There are like. no immunities(especially defensive) in this metagame other than Corviknight(maybe Dragonite, Rotoms, Bronzong, but these last two don't feel particularly viable). Teams without Corviknight are imo at least somewhat weak to Great Tusk/Iron Treads/the move Earthquake. Yes, there are viable grass types, like Breloom, Meowscarada, and Wo-Chien, but the former two are frail as shit and the latter is slow and susceptible to the megahorn that the donphans have. Part of the problem is that the existing immunities not named corviknight don't have the typings/aren't bulky enough to function in this metagame but i also generally feel like mons like lando/torn/zap or to a lesser extent buzz/rilla/tang existing in last gen really helped a lot in this regard. This lack of immunities obviously manifest itself in terms of a weakness to spikes and toxic spikes to a lesser extent.
I do like that there are actual spinners not named excadrill now, but one of them is cyclizar which i can't help but feel hatred for
Revenge killing is really important
I think one of the things keeping flutter mane and roaring moon from outright flattening the team I'm running right now is that it packs 3 mons with priority(one of which also has focus sash) and scarf meowscarada. This level of prep is kind of the only counterplay i've developed over time to this really fast-paced metagame. Speed tiers normally deemed fast or at least acceptable(e.g. garchomp base 101, iron treads 106, iron moth 110, even iron valiant's 116) are starting to feel very inadequate when there are about 3-5 incredibly relevant threats that are faster than these speed tiers, let alone speed booster energy or scarf. The fact that scarf meowscarada(base 123???) is even an idea that works(for me, anyway) in any capacity just for outspeeding faster mons and +1 roaring moon/cyclizar is kinda telling of the type of metagame this is, in my opinion.
F for scald, defog, lando, and other forms of defensive play; we miss you :(
I have some more miscellaneous thoughts about individual pokemon that I'll leave off at least for now given that this post is already quite long, but hopefully my points make some sense! I'm still enjoying the insanity of this meta, but definitely appreciate the needed tiering action.
yet? I tried to do Tera Rock with Rocky Payload and Stone Edge but it isn't doing enough. Seems like an interesting mon but perhaps not OU material.
