The point is to drop the “Unity look” with a left side launcher and a top panel, that doesn’t hold the app menus as in Unity. Neither the Unity Launcher nor the Unity top panel can be recreated in Ubuntu Gnome shell. The Gnome apps don’t have a top app menu, so the matter of the global menu is simply not there. Therefore, a top panel as such is not needed on the screen.
EDIT: Below is Manjaro Gnome with D2P vertical panel. It came with D2D that looked more like today’s Ubuntu default. But with D2P vertical, things get equalised.
The categories, you see here is not Manjaro default.