Why did UI's turn from practical to form over function?
E.g. Office 2003 vs Microsoft 365
It's easy to remember where everything is with a toolbar and menu bar, which allows access to any option in one click and hold move.
Seriously? Big ribbon and massive padding wasting space, as well as the ribbon being clunky to use.
Why did this happen?
I'll just straight up say that the problem is with Microsoft more than anything else. Their UI design is abysmal. Nothing is consistent, nothing is smoothly animated, nothing is easily identifiable by its icon, nothing is glassy and good looking like Win7/macOS. Even in their peak design of Windows 7, they still had those awful legacy UI elements in system settings and the registry settings.
Even with multitouch trackpads being a thing on Windows now, there's STILL not linear trackpad gestures as of 6 months ago when I played with the display units in the store.
I am an IT technician working in Microsoft 365 / Azure, Microsoft makes changes so often that their own documentation hasn't even been updated with the proper new name of the product in the product's own documentation, oh and the name change took place several months if not a year ago.