There’s plenty of rap in K-pop though. A great deal of Kpop is basically cultural appropriation from black people in America, whether it’s having a group rapper or having your video be “streetwear” themed.

Meanwhile Jpop actively resists being relevant, I suspect their music companies are being run for the purpose of letting the owners hang out with women even if it’s not profitable. (Or in the case of Johnnys, underage boys.)

Jpop has moved in more artistic directions, probably because of fan tastes. Like Attrashi Gakko, who are intentionally produced to look, dance, and sing unpolished and natural (the anti K-pop band)

It's been like that for a while (like "anti-idols"). Japanese media is always unpolished and cheesy anyway, which is one reason anime is the only part anyone outside the country cares about, but the music industry does have a surprising amount of room for letting artists do whatever they want as long as it works.

When I heard about Atarashii Gakkou I thought it was some kind of American fan group because the name sounds like it was Google translated… guess it's just unpolished too.

I'm not sure if the unpolished aspect is intentionally produced or genuine. I would bet on the former, that...they intentionally take idol quality girls and go plain on the clothes and makeup for that "girl next door" look.

it's just Japanese consumer don't prefer rap, and songs are generally made for domestic market (until now?)