For me, that's the point.
For a program as ubiquitous as Word (and as complicated as Word), unless there were clear benefits from the new interface, it shouldn't have been changed. The change itself was the problem.
Your comment is getting at an important, fundamental UX principle: all conceptual change is inherently painful, and every time you ask a user to re-learn something you are always wasting their time, even if the new design is better.
Sometimes a UX designer looks at two interfaces as completely separate, and thinks their job is just to pick the best one. The reality is that usually UX decisions can't be separated from the current state of the app. UX design is more like surgery, and the invasiveness of the operation has to be a consideration.
Having said that, I'm mildly skeptical that the interface didn't need to be changed. The old interface for Word was extremely user-unfriendly. If you go through a few of the interviews about Ribbon[0], there was some really interesting thought put into the new approach around discoverability, and while I'm not sure I agree with all of the theory they used to justify it[1], the changes did seem to be addressing a real problem.
But I think it's debatable whether or not the discoverability benefits were worth the pain, and I think there may have been better ways to roll out the changes.
[0]: sorry, too lazy to hunt them down and link them
[1]: I am mildly skeptical of contextual menus/toolbars. They're not wrong, they just have drawbacks that people don't always consider. Sometimes it's useful to tell people what is disabled, and to give them grounded, unchanging "landmarks" in the UX that they can use orient themselves while using a program.