I have no doubt there are improved clients. But that is the problem. IRC is not standardized at all. Different clients give different results. Also, we are talking about IRC in the 80s, not today.

That’s very far away from good usability.

Original IRC also used 8bit text, so no unicode. Note I did not say ASCII, because IRC did not even defined encodings. Do you remember the pain of different Code pages on computers?

IRC as a protocol was basically a dumpster fire that somehow worked.

Don’t get me wrong, I loved IRC (using irssi on bash mostly). But I wouldn’t praise it for usability. At all. And I would never pretend IRC set standards for usability in the 80s.