But representing the DOM etc inside a 3D space is useful so you don't loose access to the world of 2D information. However there are no good solutions to this at present the Immersive Web Workgroup in W3C are looking at Layers or DOM Overlay which is for AR modes but might support 2D navigation but it seems low down on the priority list due to CORS and other security challenges.
https://github.com/immersive-web/navigation