I hope XMPP just goes away and stops distracting people from more productive avenues. It can't be fixed. It's dead. Matrix is the modern replacement. I used XMPP to implement a chat client within our application around 2012. It was a freaking nightmare. The roster system, the incompatibilities, the lack of standardized synchronization, the never-working group messaging.
Lots of good XMPP implementations disprove this.
I hope Matrix just goes away and stops distracting the FOSS community from improving existing internet standards instead of custom protocols by random startups :)