Thats a generalization, theres plenty of rappers that talk about other stuff that are both mainstream and underground. Eg Actual Proof, Drake, Self Scientific, Roots, Skyzoo etc.
You sound totally jaded and mad about Hip Hop. Maybe you should listen to another genre for about a month. I try doing this when I get bored of Hip Hop. It usually lasts about 3 days.
Bookmarks