There's so many things wrong with iTunes I can't just pick one.
But I will anyway: it's an music player, video player, media library manager, app library manager, digital book library manager, audiobook manager, podcast manager, iOS sync, backup, update and restore manager, app loader, medium for file transfer between iOS and the computer, music store, video store, app store, CD ripper, plays radio, social media app...
And the worse thing is, I know I missed a few things. Add in an url bar (it already has a browser built-in) and it could very well be a (albeit basic and utterly crappy) complete operating system.
What... the... ****?