This is techno-utopianism. The problem isn't technical. Your grandparents won't figure out how to host their own cloud or use Mastodon. Your friends who work at art galleries or in construction won't figure it out either. The reason centralized services proliferate is that they cater to the vast majority of people who don't care about this stuff.
"How do we limit the harm of misinformation while preserving our freedoms?" That's a political problem. We can't just code our way out.
This is what most people here dont seem to understand. If you are banned from Facebook/Youtube/Google/Twitter, for the mainstream public (That is, 90% of the people) you are effectively banished from the Internet. This is like a candidate not being covered in the NY Times, WP,LA Times, but it is OK because the "Quarterly Express" in "Chinook county" published a 2-pages interview.
"How do we limit the harm of misinformation while preserving our freedoms?" That's a political problem. We can't just code our way out.