TOO many bots log entire channels out to public html sites. This is prevalent in everything like discord etc but the degree to it in IRC is just ridiculous god knows what any of those 1500 bots in a channel are doing.
NO features. I'm just over the IRC client and protocol and whatever else. It won't preview gifs, you probably still have to do some xdcc crap to send a file. After using discord and twitch and anything remotely modern it just doesn't allow the same type of conversations, socializing, interactions, but a lot of people do love that about it. I don't include weird irc clients like AcidMAX or whatever would be hip nowadays that probably came from a russian warez group that now has your credit card numbers.
No syncing without running an eggdrop or some tty somewhere running it 24/7. No multi-device support, have to join the server and log in again etc. if it ever restarts or you're somewhere without a shell running it.
Everyone is just bluntly anonymous and you have no privacy outside of priv chans where you know literally everyone.
And being an op the amount of absolutely depraved and creepy stalkery stuff that went on was insane. So many of the few women who identified themselves as women would be harassed and stalked all over irc and sometimes IRL. Lots of glining of creeps.
This was very much an efnet problem with some of the communities it developed. Freenode etc I'm sure iddn't suffer that drama much if any.