Is it possible that rap is not just a genre of music…
But the evolution of music?
Granted, classical music overall is much more melodically + harmonically complex, in a strict sense – but rap even in its current youth integrates its own nascent form of musical complexity (making rhythm the centerpiece, then harmony, with melodic sampling instead of orchestral performance) with simply unmatched lyrical complexity, combining music and poetry in a single art.
Also, rap is The People’s Music – much more accessible to produce and consume than music has been when it required complex, expensive instruments and training to produce, and elite socio-political status to consume.