"I fear that many decentralised web projects are designed for censorship resistance not so much because they deliberately want to become hubs for neo-nazis, but rather out of a kind of naive utopian belief that more speech is always better. But I think we have learnt in the last decade that this is not the case."
What you should have learned in the last decade is that social networks designed around virality, engagement and "influencing" are awful for the society in the long run. But somehow now the conversation has turned away from that and towards "better moderation".
Engage your brain. Read Marshall McLuhan. The design of a medium is far more important than how it is moderated.