It feels like Mastodon is one really great third-party client away from being mainstream-ready, on the UX front at least.
The same thing happened with Twitter years ago: Third-party apps like DestroyTwitter, Tweetie (which became Twitter for iPhone), and Tweetbot helped redefine the mainstream UX of the service, in a hugely positive way. (Until Twitter shut a lot of them down, anyway, but that’s a different story…)