For the record, I also don't like Metro on a desktop PC.
FWIW, I don't think it's Metro that MS bungled, but rather how the plain old desktop, Metro, and settings were intermingled, especially in 8.0. Metro is fine for what it is: a UI designed for single / double-tasking media consumption. The default full-screen view is slick for Netflix and YouTube, while the default Mail and Calendar apps are good enough for my mom, but horrible for work needs. My biggest gripe is that the default apps for image viewing, the calculator, user settings and so on were all Metro apps -- even when launched from the desktop. One of the absolute stupidest things I've ever seen on a PC was day 2 or 3 with 8.0. I was writing an email in Outlook and wanted to double check some math. I fired up the calculator and was presented with a 22" fullscreen 4 function calculator that completely obscured the numbers I wanted to check.
Throw in how some OS settings were only available in Metro
But my issues with Metro were, by and large, focused on how I kept on being punted into it even when I most definitely did not want to be.
As for the icons? I think MS is simply going for consistency across the different flavours of device (phone, tablet, desktop). As 8.1 stands right now, it has two sets of icons, one for desktop, one for Metro. With 10's move towards windowed Metro apps, it doesn't really make much sense to maintain multiple sets of icons -- that lack of consistency, in and of itself, I believe, is poor UI design.