[southerntofu]

Funny you should mention Zoom, which just like Whatsapp is pretty much a half-baked proprietary XMPP implementation. Now if we had proper interop regulations mandating interoperability between commercial entities (no need to apply that to hobby/research projects), we could talk between all these networks.

Sure it would take a few months of serious dedication for these chat vendors to write specifications for the protocol spaghetti they came up with, but the benefits would be tremendous.

So why is "nobody" using XMPP protocol? The problem is not exactly with the specifications (although there's still a little margin for interpretation here and there, they keep evolving for the better) but rather with the implementations. Since a protocol is not tied to a single implementation, it requires additional resources to develop user-friendly clients. This fact is used by an argument by some people (see also: m0xie's The Ecosystem is moving) to justify centralizing all communications and protocol development. This argument was amply debunked by Daniel Gultsche (who maintains an Android XMPP client) and Drew Devault (who maintains an (unfederated-so-far) forge):

https://gultsch.de/objection.html

https://drewdevault.com/2018/08/08/Signal.html

There's also a lot to say about the Matrix/Element approach, which has some good and bad sides. I'm happy to elaborate if that's of interest to someone.