If a track is poorly written, and poorly produced with cheap sounds (like stock keyboard sounds), lifeless and overly midi sounding, mastered too to low or too thigh, if it’s what you might call rambling and musically incoherent (rhythmically erratic and tonally confused) it can keep you out of many libraries. On the other hand, I’ve heard tracks fitting that exact description that do, in fact, sell in at least three libraries. Go figure.