I imagine XMPP’s ease of use has likely increased since the last time you used it, probably best not to judge it on such an old experience?

Currently none of the Discord alternatives have anywhere near the install base that Discord currently has, and many of the direct clones are so new they have literally none, like Fluxer. If an existing network effect is a requirement for the people trying to leave Discord, than they will be trapped for a very long time.