90 FPS for redrawing the image according to the motion of your head, but the actual rendering of the scene can be much slower. Motion reprojection is basically the only way to make GPU-intensive games like MSFS playable in VR on < $1000 GPUs.
Retrojection is great but it can't make up for 50 fps.
For something this big and far away you'd think there would be a way to cheat.
It's not as if things are going to move massively if you move your head a bit, you should be able to precalculate things to an extent.
Most VR headsets/runtimes support this but it only goes so far. The closer things are the more occluded sections will need to be in-painted. The farther the scene is the more it might as well be a skybox at infinite distance.
Nah. Not once you are experienced. Agreed as far as beginners.