well, it's your opinion i guess and i should respect it, but i don't necessarily agree with it. see even if the instruments are incredibly easy, his chord progressions at the time were non generic and freaking catchy.
Music is an expression, a way for people to write and sing and play anything they want, he did what he wanted and got to where he was, he pioneered a SPECIFIC genre. (talking bout kurt)
I study jazz and have been playing guitar for 7 years and and going to college in music so i understand how simple their songs are but nevertheless their great.
but hey that's my opinion