re: What's the next dogshit twitter alternative

ultimately no such thing, since the core appeal of twitter is the staggering degree to which 'everyone' is there, and everyone who isn't still at least has some trust in the assumed safety of the url and will engage nonetheless.
there are more sustainable options, but those favor smaller, subject matter themes, and or  unconventional management patterns that are developed to appeal explicitly to prospective signups rather than be an "everything app"
Forums,
Reddit Boards,
Mastodon/Pleroma ActivityPup based Servers,
the list goes on.
but what you may find, when comparing the material features of Twitter is that the alternatives already exist:

Elon essentially wants to make Twitter into Facebook, but without all of the messy implications inherent in demanding all of your personal data and then freeballing how that data is handled (or so it seems, Elon doesn't seem like he'd care either way)

there is also Youtube, which has the openness of Twitter through the ability to embed and share posts/videos easily offsite,  while one may also take advantage of Community Posts and Comments to achieve the same level of communication, but with far less ease of use when it comes to locating and interacting with non-video content, it is only ever going to be supplementary to the Videos.

there is also Reddit, but Reddit by design, separates and silos off users from each other, making the appeal of engagement more focused, but also more susceptible to
user disillusionment
platform abuse
and less addicting

I could go on about what I believe to be excellent features and the killer app appeals of Activity Pub software, but I'm sure you already have opinions about those solutions, so I will save them for another time