Taste is a constantly evolving thing. I am sure we are actually already in the midst of a shift away from flat design in certain more advanced design circles. Crucifying old styles can be helpful, especially when a new design flavor is explicitly reactionary, but is it not obvious that the trend from a decade ago is no longer trendy?
I am also somewhat doubtful that flat style was tied to specifically iOS 7, as opposed to the general zeitgeist of 2013.