Why are people still on there? Twitter has been sold; the old management is never coming back. X is, almost explicitly at this point, a platform meant for crypto scammers and white supremacists, and that is not going to change. If you aren't part of or adjacent to those groups, fucking leave it.
There are a lot of informative artists and educators that are otherwise scattered to the four winds (or worse, only on Facebook/TikTok/Instagram). I've learned a lot from people posting about field work they're actively doing, people certified to do all kinds of jobs I'd never otherwise get to hear from, etc. There's not as many as there used to be, but there's enough that I'd rather see what they have to say while I'm waiting for my Bluesky invite.
Niche communities that took years to built up and that I can't find anywhere else. For example Esperanto speakers are quite active on Twitter. They also have their own Mastodon instance, but it is not the same. (I use both now)