Often shred fans ignore musical sensibility and focus more on technique and speed. I think that's what you're seeing here. I personally don't like much of Cobain's music, but not because its easy, just because its not the kind of stuff that speaks to me, but that doesn't mean I'm going to say its bad.
I'd rather listen to a good piece of music (I'm not specifying style) than a piece that requires a lot of speed and technique but really doesn't have much content in terms of melody. It's the equivalent of speaking very fast because you don't really have anything meaningful to say. This goes mostly for shred music, but theres some jazz and I suppose classical where this is the case also.