I get that, that was the whole point of that comment is the likes of us wouldn’t want to interact with Facebook but as I said that’s just an example.
Imagine the chaos if Reddit implemented activitypub, or discord with their threads feature, or even just a new instance like world that snaps up a lot of users for one reason or another, plays it safe for a while and acts benign until they’ve got the bulk of the users and then starts imposing their rules on other instances