Mumble isnt easy to use but has great voice and terrible text, matrix and irc are both -- for most non techy people -- hard to use and esentially text only, jitsi is video conferencing, xmpp is mainly not about voice and suffers the same issues as matrix.
I really hate the state of things as I would love to contribute and join some oss communities but they only exist on matrix and I hate using it. Its one of those things i wish i had the know how to start building my self, but webrtc alone seems impenetrable for mumble/discord style audio.