Is IRC a tiny fraction of what it was? As a percentage of internet traffic sure, but has the population of IRC users actually declined?
I don't think IRC is one of those technologies whose usage count in absolute terms is at an all-time high today. It wasn't exactly mainstream in the early 2000s, but it still had lots of users.
“Here you see the 100 largest and most popular IRC networks that take part in netsplit.de's comparison, but please consider that there are still some big IRC networks that are out of competition"