This is a core problem of distributed systems though. Signal even cites this as their reason to not federate with anyone.

Once you get decentralization going you need everyone to stay kind of up to date or stuff will just not work.

It is not. Discord’s protocol has been tailormade to suit Discord and the developers will not give a single thought about keeping it stable because only the Discord server&client are meant to use it.

An XMPP developer would likely have been delusional about the protocol he himself developed. But at the time I can assure you XMPP was completely irrelevant. AIM/ICQ/MSN/Yahoo! and maybe IRC were the tools of the day back then.

Because of actual competition (which XMPP had absolutely no part in) multi protocol messengers had their golden age then.

No.

• I want to send messages to people who are not currently online (having a server stay online for you is a desparate hack and not a solution)
• I want to send media other than text
• I want my messages to be e2ee
• I want presence - e.g. know if someone is available, busy, away
• I want voice/video calls

and many more…

None of these were solved by IRC but by the others you mentioned.

Also Matrix can bridge to XMPP, of course you wouldn’t because nobody uses XMPP.

No. There was nothing to extend and extinguish with XMPP. It was a dead on arrival protocol that nobody ever used seriously. I’ve been to the internet at that time and what people actually used was: AIM, ICQ, MSN and possibly even Yahoo!. (IRC for the nerds and Counter-Strike)

It was exactly the other way around. Nobody ever used XMPP, then Google opened federation on their first chat and suddenly someone was actually reachable via XMPP which was a cool thing for some nerds that were into XML then, but when Google noticed that it only imports problems with nothing to gain from the XMPP network they just shut it off.

At the time nobody cared because the people accidentally using XMPP didn’t give a shit about it because they used Google not XMPP in the first place.