CG has always had problems with realism. Eye-lines are never perfect, colors between live/CG elements never quite match, reflections can be incorrect, directionally incorrect, missing, or mismatched in color/intensity, lighting color/intensity/direction is often inconsistent between the live elements and CG elements, mattes have problems at edges, motion tracking is usually off by just enough to cause odd movement discontinuities. All of this makes CG look cheap.
But there is a new approach using large displays surrounding your shooting scene – and it’s changing the game completely. Even more amazing, camera movement and simulation are done using the Unreal gaming engine. Even back in the mid 2000’s, I worked on a project that was attempting to use a game engine for movie pre-visualization. That’s how far things have come. The amazing visuals of the Mandelorian were created using this technique – and it’s blowing green-screens away.