Earlier quoted context omitted.
> XMPP was supposed to solve all those problems when it came out That's also what Matrix said it would solve when it started. Except now it's yet another protocol with its own chatrooms that are not reachable from any other protocol by default (even rooms on matrix.org); and bridges are at best in "beta" (except the Telegram bridge, which is "late beta"): https://matrix.org/bridges/
I have lots of warm and fuzzy feelings toward Matrix, but my take is that XMPP solved my basic problem over 15 years ago. The problem being: I want to talk to Alice, Bob, Mary, Jane, Fred, and Joe without having to install ICQ, AIM, and Yahoo Messenger. Or should I say Facebook, Whatsapp, and Signal? I don't know what Matrix buys me over XMPP, but at this point, I don't care. I'll gladly drink the Matrix kool-aid, as…
Matrix at least has a company pushing for it, so there's a better chance it'll have more success than XMPP; unfortunately we'll have to wait a few more years to see the difference.