I'm not saying I'd reach matrix.org levels, but I am kinda anal about having something that could reach those levels. So that my users won't experience issues. Because once you pick a matrix server implementation you are pretty much stuck with it. Migration would require a lot of hours of converting users, and might not even be possible depending on how the passwords are encrypted.
I know people who've been hosting the same XMPP server for decades. So this really shows the immaturity of Matrix. I still believe in it but it needs some more time.
Well Matrix isn't as old as XMPP yet, so no one could have possibly hosted a Matrix server for decades, but I've hosted Synapse for 5 years now and steadily getting more family/friends on that instance.
No problems so far and performance has been steadily getting better. There was a low period when performance was not up to par about two years ago, but ever since that's been fixed, it's been smooth sailing.
I'd say just stick with XMPP and extend the protocol to fit modern needs. If we want an universal chat protocol that's going to last, reinventing the wheel is not going to get us there.
I know people who've been hosting the same XMPP server for decades. So this really shows the immaturity of Matrix. I still believe in it but it needs some more time.