I play RPGs and Bioware when making Mass Effect Andromeda chose Frostbite over Unreal Engine 4. The problem with Frostbite, is that it is not designed for RPGs, and mostly for FPS games. So they had to more or less try to fit a square peg into a round hole. It caused more problems than it solved.
Imagine trying to turn a toaster into a computer. It was meant for one purpose, toasting bread. It wasn’t designed for video encoding, deep learning, or in this case flight sims.
If you want pretty graphics, I’m sure MS or Asobo could add some shaders to MSFS2020 to accomplish certain effects.