Instead of teaching the foundations (apply to all subjects) - let’s teach culture.
Example: no need to teach standard English - let’s teach Ebonics.
Funny, we were made to recite the pledge of allegiance every morning in my school. From a very early age, this sense of blind nationalistic pride (i.e. large-scale tribalism) was subtly instilled in all of us, as thing that simply should not be questioned. So basically, they force fed us "culture" every morning.
Anyway, one possible issue with teaching only the works of the "established geniuses" of the past is that it can set the bar impossibly high for the learners, based on completely arbitrary dogma. "Learn this (but be aware that nobody will ever be as good as this because my worldview does not allow for the 'greats' to ever be surpassed)."
Teach kids to approach the world with an open mind. "Genius" is often just "tons of hard work every day" in disguise. So any musician or composer who has worked hard at their craft is fair game in my opinion.
It's entirely possible to get a high school diploma (and even an undergraduate degree) without ever questioning or challenging a single thing you are taught. Then these kids grow up and, in a college classroom, 95% of them just sit silently and don't even ask questions at all, let alone question the information itself. Then we all end up stuck in the past.
As for the original topic, I don't see why teaching Stormzy et al (who is really, in my view here, just a proxy for modern music versus classical) means they can't also teach Mozart. There's room for both, and for much more. But I can say personally that if my introduction to music had been purely Mozart/classical, I would have gotten bored right away and turned to painting or sports instead. I never got into classical music until I had already been a musician for ~15 years.
"You’ve got to play with ideas that are sort of on the edge of what we know, otherwise you’re stuck with what we know." - Sir Roger Penrose