Everything is not 2D. Most of the first-party apps they've showcased are, but both the launch event and subsequent videos + documentation have shown full 3D capabilities, both in VR and MR mode of operation for both first- and third-party apps (including full build support in the Unity engine, meaning a huge number of existing VR + MR apps will be deployable on to AVP relatively quickly if developers choose to invest in porting).
HoloLens was commercially released in 2016 and its successor, the HoloLens 2 in 2019, the latter of which is still available.
And the Google Glass (not 'glasses') would not have allowed 3D in any true sense as it lacked the capability to calculate the user's head pose in space, necessary for 3- or 6-DoF tracking. It was essentially a heads up display attached to your face.
HoloLens was commercially released in 2016 and its successor, the HoloLens 2 in 2019, the latter of which is still available.
And the Google Glass (not 'glasses') would not have allowed 3D in any true sense as it lacked the capability to calculate the user's head pose in space, necessary for 3- or 6-DoF tracking. It was essentially a heads up display attached to your face.