Well, I agree with you that currently federation does not help, cause it is not used. However, XMPP is actually very easy to use protocol. It only gets hard whe

Well, I agree with you that currently federation does not help, cause it is not used. However, XMPP is actually very easy to use protocol. It only gets hard when you're building a chat application that does all sorts of things that are expected from a modern messenger. But receiving a message, replying, is easy, fast, and requires surprisingly low power. It is no coincidence why both apple and Google use a modified XMPP to power their push notifications. So supplying every 'smart' device with a capability to talk over xmpp potentially solves all interroperability issues. You just need to agree on message format, all other infrastructure is already in place.