Scientifically speaking, how many generations would it take to erase the sexual dimorphism between genders and turn average males into femboys?

Women are generally attracted to men who look like neanderthals (massive brow ridge, big maxilla, heavy jawline etc.) but since modern life doesn't require men to be physically strong or formidable, wouldn't this eventually lead to women preferring more feminine-looking men? Or would that take too long to happen naturally?