CupertinoPageRoute and MaterialPageRoute animations belong to mobile. On your Flutter web app, they look cheap. The web is click and open, with no transition animation.
That's the beauty of Material theme:context.push, context.pushNamed, and declarative routes all run through it. Nothing else to change.
Not using MaterialApp? Customize it at your router (go_router uses pageBuilder). The rule holds: native defaults on Android and iOS, even in a mobile browser, and no transition on web and desktop.