Something that most, if not all software companies don’t realise, is that unless they’re making games, most people endure their computers, they don’t enjoy them.
Computers are something they use at work, often frustrating tasks in a difficult environment.
Most people just want to get what they want done, and go home.
So Metro comes along and changes everything, everything they were used to and and learned to use.
Microsoft nor Apple understand that people just want to be left alone, they don’t want constantly changing user interface ideas, or moving things around, or changing how “Save As” works.
Windows design probably peaked at NT4 and has been downhill since then. I’d say the same for the Mac. It peaked at Snow Leopard and hasn’t really improved since, sometimes actively getting worse.
Metro offered yet another learning curve, for no benefit. Nothing was improved, nothing got better, nothing got faster or more usable.
I know a couple of people, that if it ran on modern hardware, could run a modern web browser, they’d just stick Windows 3.1 on a laptop.
Metro was just change for the sake of it, nobody actually wanted it, they were happy with Windows 7.
It also become obvious very quickly that Microsoft’s commitment to Metro just wasn’t there, users didn’t like, so developers didn’t bother to make an effort on it.
For simpler UIs, like smartphones, Metro was quite nice, I think Windows Phone 7 was one of the nicer smartphone Operating Systems around, but on a desktop it made no sense at all, and just annoyed users.