I recognize that Bluesky is at present more open than Twitter and that all of the necessary building blocks for the infra are publicly available. That's good of course.

However I think the view you expressed there is misguided. If Bluesky locked out third party infra tomorrow presumably the vast majority of people would not move. Thus vendor lockin via network effects remains. (Ie you are always free to leave but you'd be moving from a metropolis to a backwater.)

The only scenario where this isn't true is one where no more than a few percent of the people you interact with reside on any given node. By that metric small AP nodes pass while large ones such as the flagship Mastodon node fail. Similarly Gmail and Outlook fail while any self hosted mail server passes.

It's not an easy problem to solve.

There would be a revolt if Bluesky did that and doubt they will be so self-destructive.

I'd rather be optimistic than nihilistic about it. It's still early and there are a lot of good things happening.