Camera quality is the easy problem. The hard problems are getting camera latency down and dealing with depth of field and all the other things you lose when you replace the incoming light field with camera images.
I’m pretty impressed with the depth of field the Quest is able to develop in Passthrough+ mode just using the 4 wide field tracking cameras and a smartphone processor from 3 years ago. A residual, after-thought capability like that on a $400 device is pretty impressive, IMHO.