I didn't mean that there is an exact list of what art is crap; I meant that for any given person, most art is crap to them.
For example, for a 14 year old teenybopper girl, probably almost everything I listen to is "crap". To her, Boris and NMH and Public Enemy and Willie Nelson are all "crap".
What I'm saying is that, no matter what your musical tastes are, by sheer volume most music you encounter will seem "crappy" to you.