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?
Yes they are, UX designers are not asked to make more efficient or usable designs, they are asked to make designs that "look good" in marketing, support ad integration, hook people into others services provided by that same company, make it more difficult to incorporate with workflows that include third-party applications, etc.
This is deliberate UX design, which is part of the enshittification process.
You are thinking of an entirely different thing.
If you put the same amount of ads in software that looks like it's from the 90s, do you still think you'd like that 90s software? Of course you wouldn't.