No persistent presence, no true source-of-truth logging, bad authentiation - I mean, there's really nothing good about IRC unless you have a fetish for late '90s tech.
Nothing like firing up google to search for where you might find the chat for the server you happened to connect to so you can see what you missed while you were away or disconnected while waiting for someone in a different timezone to respond.
It supports encryption but navigating what your client supports vs what the server supports is sufficiently finnicky that it can easily eat 5-10 minutes trying to set up, vs. plaintext which is easy. If someone non-technical had to get in, I'm not sure they could figure out enabling encryption on IRC in e.g. Pidgin which I've found to be a great client.
