Material design is more than just the colors, shadows and spacing, its also the animations and interactions.

This CSS framework fails to replicate things like "ink" that fills an element with a tap color based on where in that element you tapped.

Or the way that a block of color slides across the input when you focus it and the placeholder slides up and scales down to turn into a label.

Material design is not a CSS theme, it requires many other interaction and animation aspects that the Polymer project is building out with their paper-* components.