SMS is about as close as exists for open instant messaging, but it requires a phone number
IRC seems to have inspired Discord and Slack, with the closed variants improving on features and discoverability.
As far as I know, XMPP doesn't really have a cross-server ability like SMS and IRC, though.
E-mail is totally intercompatible, but the experience for anything apart from "the equivalent of letters" is simply horrendous. Delta Chat tries to make e-mail more like a chat app, but it isn't perfect, because e-mail wasn't designed to be a chat application.
XMPP has other massive usability flaws. So does IRC, Matrix, and others.
Meanwhile the clients Element built to bootstrap the protocol have been stuck paying off huge amounts of product debt, and are finally at the point now of surpassing mainstream apps - eg https://element.io/blog/element-x-ignition/ - but it took years longer than it should have to get there. Again, it’s not the protocol’s fault though, other than the extent to which building a protocol draws energy from building killer apps.
Edit: there was also a time when AIM could send and receive SMS due to this structure, and at one point it was trivial to set up a script to email your phone number as SMS for alerts and such. This became more complicated as SMS providers started to require a lot of the same stuff as email providers to cut down on spam.