...feels, to me, like a huge mistake.
How would one eliminate hate speech and toxic content from it? Or illegal content? Or anything you put there and need removed to keep living your life freely? The technologists developing this tech hand-wave these concerns away citing "freedom of speech" -- but one's freedom ends where another's begins, and hate speech, toxic content, illegal content, not being able to have what you said or did forgotten online, all these things curtail someone's freedom.
And by making it decentralised, they're just making it harder for people who are the victims of these problems to hold the people responsible accountable and to stop them. These technologists want freedom of speech at the expense of everyone else's freedom.