IRCv3 the "next gen" version of IRC is woefully inadequate compared to Matrix. The IRC working group is only worried about the IRC client protocol and the effort seems to have largely stalled. That's like defining the protocol for Lemmy servers and clients without the Lemmy server to server communication.

https://ircv3.net/wg

XMPP is a potentially more compelling option/a good option. I don't know enough about the low level details to really debate whether XMPP is "better or worse."

I don't think either of these protocols being older qualifies them for superiority on the merits of "standing the test of time."