Twitter became Twitter by branding functionality that everyone with an email address already had access to, and slapping a simpler interface on it. Could that be replicated? The historical success of innumerable chat startups suggest it could be.

The successor to Twitter has an advantage that Twitter didn't have, which is an existing social graph ready to migrate. If a critical mass of the Twitter graph moves to Mastodon, and the interface and experience can be made as simple as Twitter, it has a chance.

> 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.