I've often thought that what we need is a social network. You only see your friends, and your friends' friends, and so on. With tools for blocking branches of the graph and restricting views to those friends. All controlled by signed content. A blockchain without the "chain" bit, I guess.
The devil is in the details, of course. Is it even possible to thread the needle of usability and controlling your own data/algorithm? Maybe! But if there's going to be a human island, I think this is the way. Individual trusted connections branching out from you.
Bluesky does most of this. One big miss is the lack of private accounts though.
And the "block" in "blockchain" is a different sense of the word from how you block users on social media, so I don't think it bears any resemblance to blockchain. It sounds more like email (or another similarly federated network) with a whitelist.
What I mean is it would involve cryptographic signing to keep your data in "your network". Your friends can always download and share an image you've posted, of course, but it wouldn't be just stored out in the open somewhere. Content you post could only be unlocked by a key from your network. Threaded discussion could be limited to just a set of friends you choose, and their friends, by limiting the keys you distribute as part of the first post.
So blockchain has some similarities in that it allows a decentralized way of managing communication through cryptographic signing, but the core of blockchain is that it provides a full "chain" of transactions going back to the beginning of time, whereas this idea is less "chainy" and more of a graph, or maybe a bunch of little chains, each originating from your profile
The devil is in the details, of course. Is it even possible to thread the needle of usability and controlling your own data/algorithm? Maybe! But if there's going to be a human island, I think this is the way. Individual trusted connections branching out from you.