with UI I meant user interface, but also to some degree feature set. I know they want to have it modern, but the charm of IRC to me is that it's a simple stream of text messages. No 'answering' to specific messages, URL previews, reacting to messages with smileys and a thumbs up, et cetera. Also quite a few of the clients listed on the official website are inactive or as of now "incomplete" (aren't yet full featured), so in the end I went with the official client (as it seemed the best bet to just try it).
A simpler client would do away with some of it, but some of my complaints have to do with the features the protocol implements rather than the client.