I can’t help you but I just came here to say that I also very much dislike the trend that everything has to look flat. Imho visual, simulated depth (through shadows, gradients, etc.) can make UIs look actually much cleaner, because hierarchy, grouping of elements and differentiation between buttons/text inputs and non-interactive elements is often much more obvious on first sight.

Seriously though, why? Is there historic reasons for that? Did they have to pay extra for more letters back in the day?

Um actually… Opera and Edge weren’t always based on chromium!