A lot of the CG done for the 1997 SE wasn’t even rendered in HD. Many of the elements were rendered in 480p due to budget and time. Nothing was rendered higher than 1080p. The negative was restored along with many of the original separate elements. The problem is that every re-composited shot in all 3 films were only done in 1080p. The elements were scanned @1080p, digitally re-composited into the computer, sharpening filters applied and then laser printed back onto film. The resolution of those shots is stuck @1080p.
Sure, but the resolution wasn’t there in the first place, because the optical compositing severely degrades the image quality. In any case for the 4K release the effects shots were rendered at 4K resolution.
Only the added stuff done for the 2004/11 versions were redone (most but not all) for the 2019/20 Disney+/UHD releases . All of the original 1997 additions remain the same. There is a reason why ROTJ looks much better than the other two films. That’s the one that was the least tampered with digitally. 4K Star Wars looks like crap in many addition or digitally re-composited shots when compared to shots that haven’t been tampered with.
With the effects shot using the vistavision camera, even after optical compositing, the resolution doesn’t suffer too badly. It was the constrant handling and dupe grain that caused most of the degredation. And, if these same restored elements were digitally scanned and re-composited today, they would look amazing. better than any shot redone for the SE
Sure, and if the tons of films that were mastered at 2K resolution over the past decades were redone at 4K, they would look amazing too. Many movies are stuck at 2K resolution or below, or in the case of effects driven films contain elements at different resolutions. Star Wars is not exceptional in that sense.