You are entitled to your opinion, however I think many would disagree that Metro was awful. It may not be that refined in its first iteration, but by wp8.1 it was pretty good. It's functional, useable, and aesthetically unique.
And don't get hung up on the hamburger/pivot example, that is just one possible way to map the hamburger menu to a more useable form for the phone. All I'm trying to illustrate is that a consistent experience across devices doesn't mean they have to use identical controls.
That's obvious. What It's not obvious, apparently, It's that any mapping implies abstraction. As the abstraction becomes more complex, It takes more time or effort to understand the mapping, and that affect other objectives for the user experience, for example, the buying process.
Microsoft has to find an equilibrium.