slack is paid, irc is a bodge on top of a bodge on top of a bodge, xmpp is rather similar, and matrix... would be nice if any of the clients except element supported any of the features, and also if message synchronization worked more than halfway
Tbh, I would not mind a proper chat standard built on activitypub, it's obvious that this protocol works, now if only somebody built a secure messaging platform with it.