But for lighting, the main problem is the BlueRay grading (the 4K scans don’t look that bad).
I’d like to agree, but can’t. RotJ has terrible lighting.
Compare shots on the SuperStarDestroyer bridge in Empire and Jedi. In Jedi, it looks like they’ve closed and gone home for the day. No lights on, no screens on, very dark, very boring. This is the same technique they used for the whole film and it makes everything look cheap.