I think the problem is that it's a style that looks great when you deal with a single screen with a few design elements but that becomes very difficult to maint

I think the problem is that it's a style that looks great when you deal with a single screen with a few design elements but that becomes very difficult to maintain when dealing with an entire app or more complex interfaces. It's like trying to typeset a book in a font face intended for catchy slogans on a leaflet.