To be honest, I think it was not that bad from a usability point-of-view, agnostic of history. People were just not used to a full-screen, search-focused start menu.
A similar thing happened with Vista, people were overwhelmed with the wildly different UI. The next version was then a slightly milder version of it, and at the same time people had gotten used to it a bit, so most were happy with Windows 7 and are now happy with Windows 10.
It's interesting to see how strongly change-averse most people are when it comes to those things.
It's interesting to see how strongly change-averse most people are when it comes to those things.