It's always seemed odd to me that on the one hand material design admits how important the physicality of an interface can be, as well as our spatial understand

It's always seemed odd to me that on the one hand material design admits how important the physicality of an interface can be, as well as our spatial understanding of it, but on the other hand tries to eliminate the most established examples of those things. Why talk about shape and depth if you then eliminate shape and depth on the most important UI widgets? I do think there's great promise to the core idea of treating data in our UIs like we'd treat, for example, pieces of paper on our desk, or pages in a book, but just more efficiently. For example I've always felt that a music app built around a paradigm of piles or boxes of songs, interacted with very physically and naturally to build playlists, would be wonderful (especially versus the current state of the iOS music app). However most of the time it's just flatness for flatness's sake, and an excuse for designers to go wild with minimalism.