Close. It’s a mess of standard addons/plugins that you have to match up, like mods in a multiplayer videogame.
Sadly for me, it’s also the only modern messenger that has decent desktop clients that don’t look like discord. But I guess that this will never change as I seem to be pretty lonely with my want of those.
The solution was nearly always to create golden packages which could be summarised.
XMPP v1 server could be just XMPP itself.
A v2 client/server includes packages for OMEMO, Websocket, Resumeable connections
A v3 client/server has packages for whatever else becomes the de jour.
The idea that you can just mix and match without ever standardising on a set of capabilities was a large part of what killed XMPP and was entirely solvable.
This is either barely getting used or not used enough (or maybe too hidden). Because I had only seen single XEP lists for both clients and servers I looked at.
Sadly for me, it’s also the only modern messenger that has decent desktop clients that don’t look like discord. But I guess that this will never change as I seem to be pretty lonely with my want of those.