[__david__]

I think you are confusing composing with performing. A composer doesn't need to be able to play an instrument to compose music for it. Composing hip-hop tracks doesn't mean that you need to be a skilled performer of a musical instrument—but it still means you need to be a skilled musician. You aren't just going to throw 20 seconds of some nonsense together and then loop it over a whole track and come away with something that stands up to what a skilled producer can make.

Also, criticizing hip-hop for having repetitive background music is kind of like criticizing Bach's Prelude in C Major for having no rhythmic variation—it may be true but it's completely missing the point.