Rounded corners are an invisible mask on the application windows that the application has to go out of its way to detect, they existed in XP which these days is

Rounded corners are an invisible mask on the application windows that the application has to go out of its way to detect, they existed in XP which these days is hailed as the pinnacle of design, how are they an issue? Apart from that it looks different from straight corners. How do you expect Microsoft to sell a new Windows version if it looks exactly the same as it did before?