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.

Thanks for the corrections. I didn't realize how behind/mistaken I was on this tech

Why would everything be 2D?

It has two displays, one per eye, it should be able to show real 3D even with a broken focus/unnatural focus

I'm not saying it is limited to 2D, rather that they missed out by using something that can render 3D to only render 2D objects. Everything they showed off was just apps with layers at the most. When they showed the recreation of the guy, I thought that would be 3D, but they still distilled him into a 2D box

They have presented consuming home-made 3D photos and videos as one of the headlining features and they are already shipping 3D cameras in some of the new iPhones.

It can run 2D apps, but it isn't limited to 2D. You can build 3D experiences that interact with the space you are in or fully enclosed 3D VR experiences.

Vision Pro is stereoscopic and can interact with the environment using ARkit