First they remove the borders and only the active window has a drop shadow. Then suddenly all windows have a drop shadow and the active window has a more pronounced drop shadow (btw why add them back at all? Drop shadows are skeumorphic - blasphemy. Maybe they realized some of it actually had a real purpose - surprise!). Now we discover drop shadows alone are useless when you have a dark background. Oops, back to the drawing board...
This is what you get when you have UI designers that no longer have a clue what they are doing. I've seen so many iterations of them trying to make a mobile UI work on the desktop that it is clear they are completely directionless. At this point it has degenerated into simply throwing spaghetti at the wall to see if anything works.
Did anyone really complain about the Win 7 UI, which itself is a product of ~25 years of careful UI refinement. Enough complaining that we instead needed to end up with this disaster?
Seriously, these are not the kinds of discussions we should be having with a desktop OS that has already been hugely successful over a long period of time.