The ribbon really isn't the same thing as a flat look. The two are totally independent of one another. Take a look at this screenshot, for example: Windows 7 with visual styles turned off—no doubt familiar to anyone who's managed a recent Windows Server or used RDP. It's still full of the newfangled conveniences you loathe, despite being cast in traditional 90s bezels.
This is the point where the holier-than-thou crowd says you should know all the hotkey combinations for everything if you want to be efficient. Those never changed, creating a nightmare for anyone who wants to learn them in the post-ribbon Word.
Almost all of the biggest offenders were iOS apps, so if you never had an iPhone you were spared the vast majority of incidents where skeuomorphism caused problems. Ideally, you're right, skeuomorphism should be helpful, but many designers used it to create the illusion of quality by borrowing images and textures from physical objects that they perceived as being valuable. Here is a thorough breakdown of the nausea of the era.
It's a little sharper than that—the current generation of interface designs was a direct reaction to the previous decade's tradition of absurd skeuomorphism. The moment Steve Jobs died, Apple did an about-face and started following Microsoft's Win8/Modern/Metro UI lead. It may look like a step backward to those who from the Windows 2000 and Gnome 2 era, since there's a loss of visual cues, but the flatness of current interfaces is way better than what the classics became in the post-Windows XP era: bloated, overdesigned, pseudo-real-objects cluttered with mismatched shadows and conflicting perspective angles. You couldn't tell what was a button there, either! At least now there's a consistency and a return to the actual use of design guidelines.
That said, there are still a lot of cases where literacy in idioms dominates: for example, the largely inexplicable convention of swiping sideways on a list to reveal 'delete' or 'edit' buttons in mobile apps. That's probably where you and the UX designers run into the most difficulty. But two decades ago, every "how-to-use-a-computer" class targeted at seniors started with how to operate a mouse—so, as I think you've already recognized, it's important to try to take these things with a grain of salt, and recognize that no one is completely objective when it comes to understanding the culture of computer operation.
//GO.SYSIN DD *, DOODAH, DOODAH