The whole Radio metro is 55% ethnic (Asian, Black, Hispanic) and another 10% to 12% first generation immigrants. That's as much as 70% who won't, in their vast majority, ever listen to more current rock.Rock.
As in, an actual rock station that plays currents, not WAXQ which is all old stuff and not WNYL which is whiny alt-pop.
WDHA in NJ and WWSK in Long Island reach some of the suburban fringes but nothing comes close to the central part of the market.
And in the "central part of the market" the percentage of non-Hispanic whites is even lower... much lower in fact.
Oh, and name a successful major market station that fits your definition of "rock". I ask, because if you ask 20 people what "rock" is you will probably get at least 15 different answers.