Paper sheets do not have controls on them. That's why "Material Design" sucks too, as all does the rest of the "flat" design fad.

Minimal visual cues, analogous (not photo-faithful) to real-world physical objects made GUIs a revolutionary advance in computer use. Both flat design and this new Apple junk (which, let's face it, is a return to hated and nonsensical skeuomorphism) ignore the very concepts that made GUIs so usable.