Both Perl and IRC have suffered heavily from a massive loss of popularity over the past decade, I can't say I'm too surprised that irc.perl.org is going the way of the dodo. I really like IRC and I'm really sorry to see it go, and I still have an irssi running full time on a handful of servers. Freenode is basically the only server that manages to maintain its user base, but even for them it's not really growing anym…
I've been trying to get back to IRC, but the clients seem dated for the most part. Do you have recommendations for something with a UI that feels reasonably modern?
Not that I think that you're wrong for wanting a more modern experience, it's clearly one of the main reasons IRC is losing traction. Some things can be solved client-side by, for instance, auto-fetching some URLs to display image links inline (although it could cause privacy concerns) but you also have limitations caused by the IRC protocol itself.
For instance IRC has no notion of "replies", if you want to quote somebody you generally copy/paste their comment and put your reply at the end. That's clearly primitive and makes it hard to find the original context.