I mean, I can literally already self-host my personal data if I want to. And there are also already forks of Bluesky (not just the client, but the server and the database) that can participate without fragmenting the network. It is not a perfect system but it's so far from where you are when you just rely on a closed app.
That's great, but also Mastodon is just there and has been for quite some time. I see no added value in Bluesky/ATProto beyond the layer of that "social as a service" which looks like a walled garden / app store of sorts in the making. I may be wrong, of course...