I still use IRC heaps! I idle on efnet just for old times sake (I hang out in #LiCe and #epic, I still maintain the LiCe IRC Script which was popular back in 1994. Yes, 25 years ago. I hang out in PfSense, Proxmox and rspamd to offer (and get) assistance with those OpenSource projects. And a number of the private trackers I use still heavily rely on IRC as a means of communication.

So yea, it's still used. But it's certainly dwindling.