Why doesn't my iOS app disable dark mode?

Simply you can add a new key UIUserInterfaceStyle in your app info.plist and set its value to Light or Dark. this will override the app default style to the value you provide.

so you don't need to bother about having it anywhere else

if #available(iOS 13, *) {
    window.overrideUserInterfaceStyle = .light
}

Should work. Call it in your AppDelegate's didFinishLaunchingWithOptions.

Change the window UserInterfaceStyle for iOS 13+ version. Just set

UIApplication.shared.changeStatusBarStyle(.light)

or

UIApplication.shared.changeStatusBarStyle(.dark)

after changing window every time.

extension UIApplication {

        enum StatusColor {

            case dark, light
        }

        func changeStatusBarStyle(_ mode: StatusColor = .light) {

            if #available(iOS 13.0, *) {

                guard let appDelegate = delegate as? AppDelegate else { return }

                var interfaceStyle: UIUserInterfaceStyle

                switch mode {
                case .dark:
                    interfaceStyle = .dark
                default:
                    interfaceStyle = .light
                }

                appDelegate.window?.overrideUserInterfaceStyle = interfaceStyle
            }
        }
    }

If any confusion please let me know.