In an ideal AR setting, everyone with a display will see everything everyone else sees. So the exact concept of Dynamicland would be completely reproducible in AR.

And you get the advantage of having optional private workspaces on top of that.

Are you thinking of VR? AR merges the virtual environment with the physical one. One fun example was that I played a Finnish board game sort of like Pictionary with a Finnish friend. All the cards were in Finnish which I don't know, but I could use my phone's AR translation app to "read" the cards in effectively real time.

AR glasses could hypothetically share a networked virtual environment, so I don't see why they couldn't be collaborative.

No, not VR. Interacting socially is better without a huge glass that covers half your face, and most importantly, covers your eyes.

Regular glasses also "cover your eyes", you are aware that AR uses transparent lenses right? They augment the world around you, they don't take away from it.

Proper AR glasses would be completely see-through and not very intrusive.