I’m not trying to shit on XMPP, but there is no denying the countless issues

There's a lot of subjectivity and emotions there. So, let's look at the facts instead: XMPP is a very simple protocol at its core. You can literally implement RFC6120 in an afternoon. But you have no reason to, because of the many existing mature implementations, which takes us to the second important aspect (IMO): "liveliness". XMPP has many well maintained client AND server implementations and a rich and dynamic ecosystem. Unlike Matrix, Zulip, RocketChat, Mattermost, … it's not pushed forward by a single entity, which severely reduces the probability and effects a bad actor might introduce. XMPP is extensible in ways that makes it more future-proof and resilient than most alternatives.

If anything gets “discovered” along these lines I hope it’s Matrix and co now instead of what XMPP has become.

Those not learning from history are doomed to repeat it, and if you ask me, Matrix is doing everything that XMPP did, but worse :) I only arrived to XMPP after fighting for the Matrix cause and deeming it a lost one. No time to elaborate, but the protocol itself is insane and its creators are experts in deception and empty promises.

Edit: more about Matrix https://programming.dev/comment/66569