You're getting downvoted by cryptobros, but you are absolutely correct, there is no good use for block chain and never will be
It's a fully public database among trustless parties. To the first point, there's no reason any database can't be made public if so desired. To the second point, for the block chain to have any meaning or value beyond itself, some authority eventually needs to interpret its contents. That authority might as well hold the database or, in trustless cases, a third party trustee. Nothing about it makes sense at a very base level, you don't even need to explain the tech because it just doesn't hold up logically.
I keep seeing people make this argument and I think we all need to realize that different people use social media in different ways.
I moved to Bluesky as well. It's where my friends went, it's where the artists and authors I follow went, it's where some of the bigger names I care to keep up with went.
Feels a little gross, I'm not gonna defend Bluesky or anything, but there are more reasons for the choice.