Someone going into the subject may not have any pre-existing knowledge of the subject (like what a tree is) and may be intending to learn it from their classes. Unless we require everyone to take a class that covers it first, you can't really guarantee that people have that knowledge. While people may have known it by necessity before, computers, for better or worse, have gotten easier to use for the average person and it's no longer essential knowledge. Or they may not have even be using a traditional desktop/laptop OS that has those concepts.

As for how it's confusing, have you seen the default UI for Google Docs/Sheets/Drive or Microsoft Office recently? Google's products default to a file view listed in most recently used order with a search bar at the top, no folders. The Microsoft Office suite defaults to saving to OneDrive without any folders. If this is all people have needed to use when growing up, is it any wonder why they never learned about hierarchical folders in a filesystem?

Eh? Nothing significant has changed about the windows file system in over a decade, at least not from a user standpoint.

Most people don’t need to muck about in ProgramData, Program Files vs Program Files (x86) is pretty minimal, though admittedly you may need to check both if you’re unsure which the app you’re using is. I suppose %appdata% has changed, and one could argue it was significant, but in all honesty the concept of local vs remote should get you where you’re going, and worst case you check both.

But the base directory structure has been pretty static for a long while now.