You seem to have completely missed tester756's point: Discord became popular because it bundled good-enough versions of all of those features with no extra hassle. No one has to keep track of which client you're using in order to decide which features you can interact with, no one has to spin up a new server for voice chat or anything else—it's handled for you automatically.

You might be comfortable stringing together a bunch of plugins for IRC in order to get the same functionality, but the average Discord user never will be.