I think ROTJ has some really strong moments, some of the best in the entire Trilogy in fact. But at the same time, it also has some of the weakest.
I agree with the above statement wholeheartedly, and I think calling it both great and terrible (especially the latter) is ridiculously hyperbolic. On the grand scene of all cinema it’s a fairly mediocre film, but to call it an awful film is IMO quite ridiculous.
As for the Ewoks;
EC Henry made a pretty good video explaining how they work within the film, and he didn’t even mention the pretty obvious themes that Lucas had been playing with since the early drafts of SW.
A Defense of Ewoks
https://www.youtube.com/watch?v=prNOwClygdI&list=PLYn2a0e2FVIKni_wHXR5CJYBnnnYH7mIB&index=22&t - from the EC Henry YouTube channel (3:30 mins long).