I disagree with you, no ones worried about Jack Harlow. He's not even the best white rapper out right now. He's just the one that they put the most marketing into and trying to recoup their loan.
These right here are the two best white rappers right now but they aren't mainstream at all. Their numbers aren't as high as other rappers that make the same music as them. I'm also pretty sure that more black people listen to them because any white person I've ever talked to don't know who they are.
This white boy is nicer than Jack Harlow too, and appeals to the mainstream more than Millyz or OT The Real. His numbers are higher than the other two but on spotify he has half the listeners of someone like Dave East.