One of the most satisfying things about the iOS platform is the affordance and tactility of the interfaces which urge and woo you into touching them.
This is the most logical UI speculation about iOS7. Designers kept on making design speculations about the iOS7 UI and stuff. They forgot one thing, usability and clarity comes before making UI “look” good.
In case of windows flat UI (Designers are in love with it, few even think its modern!), lack of affordance is the basic problem. Making something simple doesn’t mean making it minimalistic. Clearly while trying to reduce complexity and simple, Microsoft team took it way ahead and made it confusing.
Designers very often break a simple rule, they see how it looks and forget to check how it works.