> have their posts go viral into the feeds of tens of millions of (unwilling) users, it doesn't replace what makes Twitter valuable.
Excluding or severely limiting virality is the essential criterion for any Twitter replacement.
That said, though I like and use Mastodon (as I do Linux), it is just not going to get Twitter-scale mass adoption. It is not, and believing to the contrary is just obvious delusion.
Maybe post.news will. It's worth a try. But if it doesn't attenuate virality, it won't improve on Twitter enough to be worth the trouble.