> The old UI is still present in some dialogs That might be fine for the operating system. But Windows native applications come in many flavors including Win3

> The old UI is still present in some dialogs That might be fine for the operating system. But Windows native applications come in many flavors including Win32, WinForms, WPF and UWP. Then you have the Electron applications like VSCode. All of those flavors have their own look and feel so at the application level the Windows UI/UX is all over the place.