because those other artists didn't shit on the art form they're reaping money and rewards from and throwing other contemporary artists under the bus.
This seems to be a fundamental either misunderstanding or completely ignoring the point that Post Malone has proven time and time again that he doesn't actually give a fuck about hip-hop. he doesn't give a fuck about the culture, the people who created it and the language he adopted to make himself millions of dollars. he's using the imagery of black artists, a lot of whom will never be able to leave their regional fame or lack thereof while he copies their style (pathetically) and takes in millions of dollars and adoring fans while completely half assing "the work" he does. this isn't undeserved by any regards. he deserves all of the hate and vitriol he gets because he's a theif. plain and simple. other pop artists do their own thing and are completely vanilla earworm music. he isn't that.
You mark my words now. It may not be a year from now, two or five, but in the future he will take his millions of dollars, get lazer surgery to remove his face tattoo's and denounce his "wild and crazy 20's" as just a phase when he steps into the realm of country and abandons one spotlight for another.
Don't forget his "equality's gotta go both ways" line when questioned about BLM and cultural appropriation.