In my opinion the only reason ROTJ ranks three is that it was not as innovative as ANH and didn’t delve as deep into the characters as TESB. It is the finale of the trilogy. So it has a job to do and I think it nailed it. The first part of the story is wrapping up the threads of TESB. Then we get to the new part of the story and the Death Star II and the Emperor. It is a race to destroy the Death Star before the plan falls apart. And the Ewoks turn out to be cute in appearance but vicious fighters. And the greatest danger to the Rebels is another Death Star. We saw what the first one could do and they are building another, undeterred (and likely omitting the flaw that allowed the first one to be destroyed) and a bit arrogant. Lucas’s story is spot on and perfectly in line. If there is any flaw, it would be with the directing and editing.
And this whole thing was George’s story. So I really can’t fault him for making sure the story came out as he envisioned it. He had a lot of collaboration on the other two films, but the story was his and always needed to follow his vision. I think there was room for collaboration, but when you have the creative genius saying the story needed to go a particular direction, it needs to go that direction. And I think he proved that he was right. The scenes with the Emperor are powerful. The final stage of the battle with Luke and Vader is one of the most powerful sequences in all the 11 films. And far from having nothing to do, Han is responsible for destroying the shield generator and enabling Wedge and Lando to get in and destroy the Death Star. And the way the three different stories are woven together is genius and it flows so well. Sure some of the parts on Endor are a bit slower, but have you seen Star Trek The Motion Picture? ROTJ never drags. Most of it is the “faster and more intense” that Lucas was going for. I would definitely not say that ROTJ was where Star Wars went off the rails. For me that is AOTC. ROTJ very clearly finished the original trilogy and did it well. I have never found a flaw to make me think otherwise.