I think a lot of this perspective may be a matter of how old viewers were at the time they saw it. I can tell you from experience, not just my own from the early '80s but as a parent introducing my own kids to Star Wars more recently, that the darker entries like Empire Strikes Back and (later)...
As a 9-year-old at the time, I can assure you that kids went absolutely nuts for Ewoks. That movie was absolutely huge and was seen as sending out the trilogy on a triumphant finale. The bitter fanboy griping about it didn't settle in until later.
Lest we forget, Empire Strikes Back was widely disparaged when it came out, and we all have that friend who still insists that Terminator 2 is a crap sequel that "ruins" everything that was good in The Terminator (and probably has similar feelings about about Aliens).
It's more like green apples vs. red apples. The disc and streaming come from the same master, just compressed differently. The compression may account for some differences, but should not look radically different. Problems in the underlying master will be visible no matter what format you watch...
See earlier post from Michel:
Sounds like the same thing I saw on streaming, which looked more like transfer problems than compression problems. The frozen grain had the signature look of the old Lowry Digital grain management that was an issue with the earlier Blu-rays.
Personally, while I found the image quality disappointing in places, I could live with most of those issues if the movie I watched was actually STAR WARS. The far bigger issue for me is that I simply do not want to buy or own another copy of this bastardized "Special Edition" desecration of the...
I don't have the UHD Blu-ray disc, but I noted moments of aggressive digital processing (frozen grain, edge halos) in the transfer when I streamed from Disney+. I'll have to scan through it again to get time codes.
All problems that are present on the Disney+ streaming version too. Disappointing, but not surprising.
I say this meaning no offense, RAH, but I think you need to watch more than a few minutes of a movie before passing judgment.