A lot of the anime-related communities have consolidated over time to the ani.social instance. There are historical reasons for this (largely due to hostility from the ml admins), and if you want a brief history for just the general anime community, I previously wrote a post here.
That being said, the ani.social instance has been growing with new communities being added. Here are the more active ones:
General Communities
Series-Specific Communities
- !dungeonmeshi@ani.social - Delicious in Dungeon community
- !frieren@ani.social - Frieren: Beyond Journey's End community
- !nokotan@ani.social - My Deer Friend Nokotan community (currently airing show)
- !dandadan@ani.social - Dan Da Dan community (show airs this fall)
- !dragonball@ani.social - Dragonball community
Misc.
- !vocaloid@ani.social - Very new community just started by @hisao@ani.social about vocaloids. Check it out!
- !vtubervids@ani.social - Community to discuss and share videos from and about vtubers
- !seiyuu@ani.social - Community about Japanese voice actors behind the scenes
Obligatory shoutout to !anime@ani.social if you want a more anime-focused discussion. Of what I have watched (or seen enough of to make a judgement) there are a couple standouts. Note that I haven't really watched much western animation in recent years.
Wildcard answer would be Star Wars Visions. Each episode is done by a different animation studio, so it can be up to personal preference as to which ones you like, but there are some great showcases in the show.
Edit: If you care a lot about animation quality, I would recommend checking out the SakugaBlog. It goes into deep dives on Japanese animation. For example, they did a whole running series on Frieren (link to the first article).