I'm a little sour about Google Cardboard. It was and still is the greatest accessible 3 DoF VR implementation in my opinion. What a fantastic concept.
I showed it to my daughter the other day and she was really impressed. There's only one remaining app that can use it afaik.
The Sketchfab viewer still supports Cardboard: https://sketchfab.com/models/45f5e56887f44075bbf283977c99541...
The older Google Cardboard on the other side got open sourced and is still somewhat alive, works on modern phones and even the Youtube app still has support for it. It is however not getting any attention from developers, since everybody that cares about VR has long moved on to Quest or given up on VR. Cardboard due to not having controller and limited to 3DOF was a dead end.