Ahahahahahha no no, you're fine, especially if it was bandom or Kpop fandom. I was in a band, but it was never a super famous one, so while I would know if the music theory stuff was wrong, I certainly wouldn't know about travel or their schedules or commitments, so that stuff doesn't bother me. And most people don't really talk music theory in their music AUs, it's just vague stuff about rhythm or melody or whatever, and that's fine! As long as you're not talking specifics, it's all good. It's the schedules, the requirements, the amount of free time you have when you're music students at a conservatory that drives me nuts. Not knowing what rehearsals are like, how they're organized. In classical music, that stuff absolutely makes me crazy. Pop/rock band AUs I can ignore with the best of them.

And agreed - I have read terrible music AUs because the story was just that compelling! So there are exceptions to every rule. :D And I read all kinds of other stuff that's just... not realistic (the number of people that make twenty-somethings CFOs, CEOs, or even just directors of offices is hilarious - that's simply not a thing that happens - but I don't care because the story is good!).