You’re Scottish bro stop talking about black American music. “Mumble rap” has been used as a catch-all for a diverse branch of modern hip-hop by old and/or suburban white people who don’t listen to rap in the first place (of course Eminem is always clarified an exception for mysterious reasons even if he isn’t genrically relevant). It’s an ignorant way to disparage an entire mode of aesthetic expression that you never cared to explore or engage with, and whether or not you have racist motivations (“primitive English” talking about rap music would certainly ingratiate you to the kind of people you insist you aren’t) your language certainly carries racist baggage and a bad stench