Cool, we've jumped right into "if you want to be independent from FaceAppAmaGooMicroTwitBookTube, it's just because you're a right-wing fascist plotting an attack." Way to go everyone.
Deplatforming by the major social platforms is actually a way for them to create a moat. The field is now salted with toxic lunatics looking for a platform. Anyone who tries to stand up another social will instantly be inundated by them, and their presence will drive everyone else away and back into the arms of the incumbents.
Social is now like a zombie flick. There are walled gardens where it is safe, but outside stalk the walking dead. Trying to build another shelter is an exercise in repelling the undead long enough to get some walls up.
There are a few other social niches that could be addressed without catering specifically to that crowd, and a few even have attractive enterprise-y plays attached that leverage various privacy-focused value propositions. Pseudonymity, for example, isn't usually given enough attention IMO (SecureDrop is a notable exception to this).