That's pretty much the opposite problem of what the GP is asking about.

I’m not sure I follow. Almost any time there is an issue with a large social network folks on HN say decentralization needs to happen to fix it. But how do you “fix it” while still having the same or better user experience?

It’s a very difficult problem to solve and I don’t think saying “make it decentralized! Make it live on a protocol!” is useful without the extensive “how” that everyone seems to ignore.

So utopia is a completely decentralized uncensorable network where basically anything goes? Not wholly achievable probably because of DNS etc. but you could come close. Not an unsupportable position but you probably amp up the underlying issues Facebook is trying to address by 10x.

Are there examples of decentralized/unmoderated platforms with similar popularity (= success for the purpose of this conversation) to Facebook?

I suspect reddit is the best example of blending "something for everybody" with "default users don't see offensive things", while also being able to remove things like the content in the story, but obviously they still have human moderators.

I think the ultra-open / libertarian model is fundamentally incompatible with broad acceptance, personally [1], but I'm happy to be proven wrong. Early IRC/BBSes aren't very convincing to me because even if they were unmoderated the barrier to entry (knowledge, hardware) was high enough to limit adoption.

[1]: I think sites like Gab indicate that even if you clone a successful product and market it as "<x> but with free speech", the free speech part winds up being a negative factor, concentrating elements that will scare off mainstream users.