The "Metro" was also optimized for keyboards
Metro supported keyboards (to an extend) but I wouldn't say it was "optimized" for it. Even some Metro apps, like Netflix, couldn't be controlled by the keyboard. That one kept me from using the Netflix app on Windows 8 as a HTPC solution.
The Metro interface was not optimized for mouse operations; it was a touch UI you could "touch" with a mouse. All apps were full screen. UI elements were hidden and meant to be swiped from the sides of the screen. Nothing about Metro seemed to be optimized for the desktop.
But thankfully you could completely switch modes and have a regular Windows 7-like desktop experience. When I ran Windows 8.1 it booted straight to the desktop, I used ClassicShell for the start menu, and I never saw a single metro app.
With Windows 10 can run metro applications in regular desktop windows as well as switch to tablet mode and run regular desktop applications and metro apps full screen or tiled.