@clacke Mozilla bundles quite a bit of unnecessary crap with their browser, so I don't value their opinion quite as much as I wish I could.
I use unrealircd, which is under active development.
In general, when I hear "irc has drawbacks" that's all I hear, I never hear what they are, and if questioned, the person backpedals like _mad_ to get away from actually having to say they can't only use text to speak to others, they need to be able to post gifs and memes to express themselves.
Last time I tried to use Matrix, I was directed to Google Captcha. Fsck that.
I ran an xmpp server for a bit, but as the number of people using it was exactly 1, and that person was available on irc, I stopped wasting my time with that.
We use rocketchat at work, and I wish the admins would install the irssi support for it so I could have a proper interface, but... oh well (: