Not iOS , but on MacOS, I hate window design in recent versions. The old versions had a clear distinction between single contents and the great/darker ‘chrome’ that made up the window header and toolbar.

These days everything is a blinding white (in daylight mode) both virtually no contrast between the two.

With multiple overlapping windows it is a complete pain to use. Loads of times I’ve gone yo grab the top of a window, only to hit the window behind and above.

Form over function.

I didn’t realise how bad it was until I used my wife’s old Mac running an old version of the OS and everything was just easier