I also don't think anybody would choose to be censored, that doesn't make sense. Maybe you could offer optional spam or misinformation filters, but why would anybody force them one themselves? Twitter and Facebook also employ "fact checking services", which would simply be applied voluntarily to other networks.
I also think the problem is way overblown. On Twitter you can choose who to follow. If select the right people, you won't get the misinformation spam.
I never claimed a replacement could be built in a weekend, and the incentives are exactly part of the problem and part of my question. It seems technically possible to built something like Twitter on a distributed basis with nobody having centralized control, but it probably wouldn't be as snappy as Twitter. People stay on Twitter out of convenience, and also because of the network effect. You would have to make lots of people switch at the same time. That is the challenge.