Just FYI when I say tasteless, I mean shallow and tacky. As I've said before, the music sticks out as egregiously tasteless. They put no effort into learning about guitars, or music in general. And it shows, repeatedly. I cited a couple that I remembered off the top of my head, a couple really blatantly sloppy mistakes. Every time they brought up music, I remember there being similar mistakes. It shows a complete disregard for guitar and music because much of it should have been obvious had anyone on staff played guitar or had talked to someone who did. To me, it seems like one of the reasons for adapting K-ON is that the episode in which Haruhi played guitar and the song she played turned out to be really popular, so they decided to do a series where they could do that multiple times. It seems like a transparent cash grab and pandering to me, just like the army stuff in the Transformers.
I think this is more of an expectations vs. reality thing, K-On is adapted from a 4koma which is primarily about the daily lives of high school girls that just so happen to establish a light music club, its relation to music is always tenuous at best. Sure they do play music, and it's about their club but its a light music club run by teenagers that have fairly lofty goals but never take it too seriously. The show doesn't take itself all that seriously either and when it does it's more about the then established relationships between the characters and on their high school life together.
tl;dr I think you're taking the music aspect of K-On way too seriously.