Microsoft has completely stripped Office for Mac of any ability to customize. Even the quick access toolbar—a feature created solely for customization—is not customizable on the Mac version. As someone who depends upon easy access to shortcuts and specialized features, this is a deal-breaker. You can't even set custom keyboard shortcuts anymore, and since many menu items have been killed off because they're in the ribbon, you can't even set them in the Mac System Preferences.
It's as if Microsoft set about to intentionally kill any possible convenience in using the apps, save for their ribbon. Don't get me wrong, I like the ribbon, but to take away ALL customization is the stupidest thing I can imagine for these apps. But hey, now the selected cell border is annoyingly and meaninglessly animated—in a way you can't turn off—so, woohoo.
In short, par for the course for Microsoft.