Every time this has been tried before, it's failed. As has been said, when we used it in the past, everyone hated it. It had a lot of problems. It was very difficult to use and it was completely inaccessible to most people because they couldn't understand it. And when you did get in, usually you couldn't use your username or anything close to it because it was actually on a much larger server, Paradox, than just Hyrule.net and usernames are server wide and almost everything you could think of was already taken. So when you talked on there people wouldn't know who you were and you wouldn't know who they were. It was overall very sloppy and unpleasent and going back to it would be a mistake.
Overall.... an IRC would be the same to a modern shoutbox or IM as Windows DOS would be to Windows XP. Some of the same core elements are still there, but it a much more user-accessible form without the crippling restrictions present in the original. Just as there's no sane reason to go back to Windows DOS when you have the modern OSes, there's no sane reason to go back to IRC since what is already used is just a much more modernized and efficient version of the same concept with a much more useful GUI instead of relying on pure text commands that even the best have to constantly look up. The only real reason anyone goes with IRC is the same one for anyone still using DOS commands, nostalgia. There is no benefit in doing it. You'll only cripple the community's ability to communicate and alienate almost everyone.