Matrix isn't an IETF spec, and nor was XMPP until 2011 - 13 years after XMPP/Jabber was created. Matrix is 6 years old.

Meanwhile, https://matrix.org/foundation is effectively its own standards body, and once Matrix is more mature I hope it'll end up being ratified by IETF or similar too.

In terms of "XMPP not being adequately improved" - XMPP is a very different proposition to Matrix. Matrix is all about replicating conversation history around the place. XMPP is message passing and pubsub.

It's extension story was fragmented, and there wasn't enough of a consensus (different actors had very different use cases) to pull it back together.

Chat needs a stronger guiding body to keep it corralled. It's too easy and tempting to extend in incompatible ways.

Well it isn't like XMPP has died or something. There are hundreds of servers and lots of clients. Having the Matrix project doesn't take away from that in any way. If Matrix becomes popular then it could supersede XMPP which is OK.

Right now it is federated vs everything else really. There is no reason to think that Matrix is suddenly going to be used by regular people where XMPP was not. The bigger issue here can't be solved by purely technical means.

XMPP has made huge improvements in the last few years. Ejabberd supports most XEPs you could wish for. Gajim on Desktop, Conversations on Android and Monal on iOS make use of those new features.

Matrix is not.

The sad irony is that the Matrix protocol was sold as a much simpler alternative to the bloated XMPP...

...and now it's bloated as well.