There is no "menu interface". You simply hide content of ribbons, leaving tabs
at top of window. When you click on tab, it's content in "ribbon-form" will
appear.
If you want old menu in MS Office post-2007, you must buy some third party
extension.
While it might be good idea to give users choice about interface they like, MS
is definitely not giving it their users (but MS never promised to be about
choice, so it's hardly an accusation).