That just Jack shilling his new Bitcoin company.

It's literally impossible for a system run by a single company to not be centralized. Dorsey acknowledging that or not does not change that nor would having some other owner.

It's actually possible (although not easy by any stretch) for us to build a decentralized Twitter that would not be controlled by a company for profit and would be more censorship resistant. It probably will not happen because of ignorance and political manipulations rather than hard technical limitations.

If only there was some sort of "user network" which could just be some sort of distributed posting service where a rotating group of companies would host the posts (more than one host for both fault tolerance and avoiding a single point vulnerability). People could post to discussion groups about the news (or "newsgroups" for short). Perhaps it would be so attractive that ISPs would advertise access to portions of this posting service and provide support for its hosting.

Something like that seems like it would be simple enough we could have had it decades ago. If only someone had thought of it then...

If only someone had thought of a way to monetize it so that Google would not purchase it and later run roughshod over it before letting it fall into disuse.

Isn't that what Mastodon, or various projects using Mastodon, are trying to do anyway? It's not such a thing can't be built, it's just it's unlikely for such a project to gain mass adoption.

Right, just like Bitcoin, Ethereum, IPFS, RSS, HTTP -- open protocols have no chance of significant adoption.

I'm talking about social media specifically here. Good luck with trying to get a blockchain-powered project up with mass adoption in that space. Maybe you can include a messenger feature running Matrix in it, too.