I think this is the most likely and best path. There's no stopping the flood of bots, the dead internet theory is beyond just a theory at this point.

Best we can do, for the internet and ourselves, is to move away from it and into smaller networks that can be more effectively moderated, and where there is still a level of "human verification" before someone gets invited to participate.

I don't like what that will do to being able to find information publicly, though. The big advantage of internet forums (that have all but disappeared into private discords) is search ability/discoverability. Ran into a problem, or have a question about some super niche project or hobby? Good chance someone else on the net also has it and made a post about it somewhere, and the post & answers are public.

Moving more and more into private communities removes that, and that is a great loss IMO.

The utility of those larger sites is coming to an end, but most people aren't discerning or ambitious enough to leave and seek out the smaller places you mentioned. Places like this will remain but will join Facebook, Reddit, and Twitter as shadows of their prior useful selves. The smaller, better sites won't have to worry about attracting the masses and therefore worsening, because the masses have finally settled.