I'm just saying in my opinion the subgenre label of J-Rock is unnecessary. And I can say with certainty there's plenty of western alt-rock bands that can keep up with Japanese bands.
It's kind of interesting to see when bands like The Strokes came out with their brand of mathy-alt rock, just how many J-bands in the early and mid 2000s literally lifted their riffs right out of the tablature XD
Besides. Music quality is subjective
But. J bands to tend to have more experimentation within the subgenres, which is also very cool.