I'd add that there are more user cohorts than you describe. There are the scrollers that just want a constantly changing feed to "engage" with (typically though not always, showing little discretion about whom they follow), there are the "industrial producers" (whether corporates or individuals) who want the world to benefit from their wisdom (showing little to no discretion about who follows them - the more the merrier), and there are the "communitarians", who want to actively engage with a more narrowly defined set of the tribes they are members of (showing greater discretion in their social graph, and also taking part in providing tribe-relevant content).
Of the three cohorots, the latter is by far the smallest (my own guess), and these are definitely (from my experience) finding homes on Mastodon (tribe-specific servers).
A lot of LGBT twitter tribe are not going to move to a site where they have to post under their government name, for their own safety.
(A very important axis for social networks is the "IRL or not" one; Facebook and Linkedin are "IRL", Twitter and Mastodon are very definitely not. Which way is Threads going to go?)
Good points. The question therefore becomes what persuades advertisers to spend money on there and so what will drive a critical mass of users and content to get to that point. No doubt the "industrial producers" and the peddlers of dopamine and outrage will be what gets the platform there.
Of the three cohorots, the latter is by far the smallest (my own guess), and these are definitely (from my experience) finding homes on Mastodon (tribe-specific servers).