XMPP has existed since 1999, but has only seen mainstream adoption inside walled garden apps that never supported federation or shut it off early on. It was possible to use Facebook and Google chat from a generic XMPP client for a long time.
See, the discontinuity is at the App Store and mobile shift. It was iPhone and App Store that destroyed equal human right to code and run, turning it into elite privilege to profit by code. And the escape hatch known as the Web is slowly closing.
Mastodon and RCS are lightyears from consolidating X/whatsapp/messenger/telegram/signal/discord/slack/teams/etc.
Email+notifications is a joke, lacking groups features, true undo, large attachments and video codecs, etc.