I don't get this, it is working. It's largely replaced IRC in open source spaces. It's not going to penetrate the mainstream but it's fine for what it is and people do use it all the time.
replyPeople have different definitions for "working". I assume that the people who claim that Matrix doesn't work are the ones comparing to alternative commercial solutions and all the polish that usually accompanies those.
replyA decade ago Moxie Marlinspike argued[1] that to develop Signal more quickly, he and his team could not be distracted by federation. At the time I wasn't sure what to think, but it does seem that the effort level of using the integrated approach of client/server/protocol may just logistically be easier.
I've been using it for years now, it's working just fine for me. It's no Discord or WhatsApp just yet, but it's lacking about a couple hundred million dollars of investment for that to happen to any open source chat solution.
replyI'll happily move over to XMPP or IRCv4 if they can get it right, I'm not married to the way Matrix does things. But it's good enough, open source, and federated.