It's very similar to how Twitter felt in its early years. You had to know exactly what you wanted to see (topics, people), otherwise you'd feel lost.
My family has been using Synapse since before Covid hit, including TURN server (coturn) for audio and video calls. No complaints about the UI so far, except for Element on iPhone reportedly "freezing" for a few moments when sending messages - and that was over a year ago.
What problems do you have getting TURN to work?
"Multimillion-dollar fines" is just another term for "pocket change" in this context. Pump those numbers up!
As someone who has written and maintained a RSS aggregator for years, I can tell you that this jankiness is in big part because of how vague and under-defined the feed formats (RDF, RSS2, Atom) are, and how "creative" various websites are in producing feeds which are just barely standard-compliant, but also just enough screwed up to cause problems when parsing them.
It was a headache after a headache trying to get all the weird corner cases handled.
I've been using Matrix for several years now, and am very happy with it, and with the progress that it made.
I have one instance just for me, which I use for general chatting, as well as for some light experiments (I'm toying with some client development and trying new plugins or appservices now and then).
I have another, private and undfederated instance for family comms. I set it up at the very beginning of the Covid-19 era, when nobody knew how long and how severe will the travel restrictions be, and we've been using it heavily ever since.
Something about books, covers and judging...
I'm not that optimistic. I think MANY people are fed up with this particular case of a centralized site being annoying, but do not really care about anything other than getting their dopamine fix, and will happily jump into sack with next big social media site, centralized or not. Most people just don't care.
Your own, obviously! Especially if you're asking in a "Selfhosted" community. :)
Mastodon does not need to scale well. Even if the userbase shrinks to what it was before the Big Twitter Exodus (or whatever you want to call it) of last year, it will be perfectly alright.
Mastodon was fun and enjoyable before. It does not need more users to remain so.