As of the time of this screenshot, I am 1st, 3rd, and 4th on ladder.
Going to go over some common threats and some underrated mons (in my opinion).
Firstly, any Shroomish users should never feel good about any win in any game ever. I used the mon to try it out and it just feels dirty
Now onto threats based on my experience in game (I use roughly the same team for every game on all 3 accounts)
Note: I don't usually post on here so I'm not gonna make those pretty sprites in the comment lmao i got no idea how to do that
Grimer-Alola: Super strong knock off, literally every single set this mon has is annoying as fuck (AV, leftovers, band, etc) paired with the right support mons. It always poisons the mons I don't want poisoned, requires a lot of maneuvering to beat
Delibird: For me, the one of my biggest threats in the tier ONLY if it is a special attack set (imo). There are a lot of physdef walls but special walls mostly consist of mons that Delibird can easily deal with with its coverage moves, albeit weaker without a form of setup, I believe it's highly underrated and deserves more usage or at least experimentation.
Ting-Lu: Among all the other non baby pokemon, Ting-Lu is rarely used, but since the majority of hazard removal in the tier is rapid spin, a tera ghost Ting Lu can set up a sweep with a fast mon extremely easily, while walling some pretty big threats (think spikes,rocks,whirlwind,eq or something similar)
Weather: The most consistent weather imo is definitely rain. Although sun can be nice and you can try simple growth sweeps with numel, against a well put together team this is far less likely. Basculegion + Kyogre is a very scary core and requires perfect play for the opponent in order to beat. I personally had to add a tera normal in my initial team building because last respects is that scary.
Overused pokemon:
Bronzor: : It is not good, just annoying.
Glimmet: ^^ Everyone with a put together team has a form of AV/spdef tank and a way to remove hazards. Glimmet isn't particularly fast and dies very easily. I think scarf is the best set but they're all not great
Pawniard: Decent, but almost always requires tera to get major value, stabs aren't great, and though sucker is nice there are a good couple mons I'm more scared to see than pawniard on the physical side.
Sinistea: I don't even see it anymore but I just wanted to reiterate that it is very bad.
Legendaries: Zacian-C and Miraidon are meta defining. Arceus is great, but all the random calm mind arceuses are awful and should not be used. Kyogre is a phenomenal rain mon, but if you're running Kyogre rain please do yourself a favor and go damp rock instead of trying to make an offensive Kyogre as your rain setter. Koraidon is good but personally less scary for me, I can definitely see people having difficulties with it though. Ting Lu is underrated. Mostly every other legendary is useless, one of the mons I listed above will do the job better for you.
I made this post in 15 minutes so a lot of mons definitely I didn't mention, if someone posts more specifics maybe I'll post my take on it but I'm too lazy to think properly about it rn.