But this doesn't change the fact that irc is obscure minority now
Agreed. I still use it when I need a quick way to chat. That and Devzat SSH chat. I can fire up NGIrcd in about 3 minutes and most of that time is dealing with LetsEncrypt. UnrealIRCD is my preferred IRCD but the configuration is more involved so I don't bother since most people moved to Discord.
Out of curiosity since I have never used Matrix, how many clients can one node/server simultaneously support approximately?