as the "pros" are the ones who will choose what OS a facility uses. The users in general won't care, and retail customers are locked in to whatever is available on the shelf when they buy a computer, unless they are "pros".

I think they objection is less that a new interface is being presented, and more a twofold objection:

1: The new interface does not scale as well to advanced use.
2: The old interface that did scale well, has been outright removed rather than sidelined or hidden by default.

The new menu is a flat non-hierarchial organizational method, which is more efficient for a small number of elements. The "old" system (as of Win7) was a fairly well organized hierarchial structure, efficient for large numbers of elements, which was paired with a flat structure (taskbar pinning) to handle quick access to the most common apps. We don't really see what reason there could have been for completely removing that system, as it could have simply been hidden by default instead. It's a departure from Microsoft's typical stance of walking a line to satisfy both pro and non-pro users, where they are now focusing on non-pro users and removing pro features.