You are right in saying that discoverability has suffered much, by hiding scrollbar and similar changes. Also, you need to move the mouse precisely to a particular spot to re-enable the scrollbars, there is little wiggle room, which may may things harder for handicapped people, older users, or people on the move (e.g. me on a train).

Or just the way the menus are on apps. Some app implement their own file/edit/view menus at the top of the app, then some will use the apple version at the top of the OS. If you plug in a TV to use as a monitor and cannot adjust the aspect ratio you're forced to blindly activate these menus as they're clipped from the screen.

MacOS folder navigation is a complete pain too, sometimes you see the list of OS folders, sometimes you see only the folder you opened in finder. If the menu is clipped due to the above aspect ratio problem, good luck getting to your home folder... No functionality to easily open a folder in terminal. Lots of basics just counter-intuitive.