I actually agree that the control panel change is annoying, though. I think it was a bad change, because it's not merely different. I think it's actually less usable.
And yes, the change from Win7 to Win8 is massive. Not a lot of people would dispute that.
However, how I interpret that statement is that it is ill-advised to over-estimate the general computer user's ability to adapt to changes, or the way 'little' changes end up disrupting the way they interact with the OS.
I might be interpreting OP's statement with my own bias, or reading into it too much, and we could probably go back and forth on semantics all day.
Regarding the control panel, I think the search functionality, which again a lot of non-techies may not even realize is an option, is the main redeeming quality and makes it much less aggravating to work with.
I agree that it is dangerous to overestimate the general user's ability to adapt to changes. Microsoft does a lot of focus groups for this very reason. I don't think that Microsoft can cripple itself by never changing the interface, though. Maintaining an identical interface might work for a while, but eventually competitors who weren't afraid to innovate on the UI would win.
I agree about the control panel as well. Search fixes a lot of the issues. I'm glad Windows 8 has kept search working (and arguably improved it).
However, for older folks, this view is not typically the norm.
I do computer repair and routinely listen to gripes about changes in Vista/7.
For instance, I often hear complaints about things like changing the theme/style settings, searching, modifying network interfaces/settings, or changes to how the control panel works.
These are often, aside from theme/network settings, an improvement, minimal, and intuitive changes IMHO.
But, to someone who is barely computer literate, even "little" things like that can represent a big change and can be very confusing.
And, of course, the change from Win7 et all -> Win8 is massive, even to me...