I don't understand this statement. One finds IRC clients everywhere. One literally has to know just one command at the beginning: /join. And then if you Google "IRC commands" or something like that, you get the rest of them easily (if your client lacks in the help area).
> the feature set's extremely limited
I don't understand this mindset. Why should a program have an extra-large set of features? Is the value of a program measured by the number of features it has?
> Had IRCv3 managed to get off the ground and made some strides towards creating a modern user experience maybe two years ago, Discord wouldn't have had such a vulnerable market open for it to stroll in and snatch up
Apples and oranges. Discord did have serious opponents named Teamspeak, Skype, Mumble and other VOIP clients - but certainly not IRC. And if my memory serves, the first thing they did was to make sure to dislodge those programs from the gamers community.