I've used IRC for a long time and still do, but I do think Discord has a nicer UX for most use cases. In particular, building communities around clusters of channels ("servers") and support for rich media (yes, some old people might call that a downside) increase the appeal for most people. It's also a lot more work to have a persistent connection on IRC (bouncers).
My main problem with Discord is that it's someone else's centralized, for-profit company and has no apparent barriers to enshittification[0]. As Reddit recently demonstrated, it's probably a mistake to build communities on top of something like that.
Matrix is a good candidate for a modern successor to IRC. It's not quite as slick a UX as Discord, but it addresses the main advantages Discord has over IRC.
Practically all of my friends grew up with IRC, we are in our late 30s, 40s, early 50s.
We might reminisce about irc but we all prefer discord.
Even the searchability of indexed irc has been surpassed by other knowledge sites. It would have to be something extremely niche these days where the only source of info is in an irc chat log
IRC doesn't even have history, one of the most basic requirements for a modern rudimentary chat app. It's ridiculous to suggest using it in 2023 when it doesn't have features a freshman homework assignment chat app has.