Mimicking a style... easy. Delivering a coherent message or story... harder. Emotional impact... even harder. IMO. But I think these are great goals for an Artistic Turing Test.
Some genres (i'm looking at you mumble rap) don't even require coherent language.
It does via the Forer Effect. The goal is to make generic statements and tell the listener that you’re talking about them (or someone just like them). Listeners then subconsciously fill in the blanks and create the most relatable impactful art imaginable.
That’s why beauty is in the eye of the beholder. You need the audience to impart the meaning ;)
Mumble rap is a totally legitimate art form. I just tend to not be a huge fan of most of the song structures and compositions, personally.
That, to me, means it could probably be generated by an AI. And I'd say the same of any genre for which repetition matters more than lyricism or storytelling. I could see a machine coming up with Lil Pump's Gucci Gang[0] much more easily than Wu Tang's Triumph[1].
“I ain’t got the surfers ‘cause I know I’m not that hard”