As a support structure providing more open communication, the fediverse might help with that. It in itself is not, and is not supposed to be, democratic
This was not my point. My point is that social media will always encourage "niches" (as you hint) and that it would be better for our politics if these overlapped with real-world communities than with, say, obscure hobbies (neutral politically) or political affiliation (the original sin of this new medium).