Hasn't (at least what I interpret to be) "material design" removed the ability of the user to determine what is clickable today? It feels like a flat colored box suffices as a "button" … sometimes. Sometimes it is really just a flat colored box, and you can't tell up until the point you click it. Buttons used to have a nice bevel around them, giving them the appearance of being … a button. Being a bump on the page that could be pushed inwards. Everything is flat now.
> Items appear to float above each other to give the idea that there is more content underneath, or that they can drill down further etc.
If I've ever seen drops shadows used to indicate anything other than just being there for looks, then it went well over my head. That seems like the most subtle, impossible to discover UI aspect. Can you show me one recent "material design" UI that uses drop shadows to convey information about the workings of the UI?