I'm aware of being able to join IRC from XMPP, but the thing that still makes IRC the best for me is actually the client selection. irssi is just leagues ahead of Gajim, Dino, Profanity, Conversations, Element, Nheko, FluffyChat, etc. I really haven't seen any chat client nearly as good as irssi besides weechat. It's like no one who made good IRC clients left IRC, so there weren't people to make good XMPP or Matrix clients.