Return of the Jedi's problem besides the added kiddie content like Ewoks and other things put in to sell action figures and vehicles, was that Lucas compressed 4 movies into one.

The original context of Luke's journey would have taken 6 films to tell. Add on the prequel trilogy and you get 9 films. I suppose the sequel trilogy other than having Luke as very old in the first episode would have been completely different from the saga of 9 films, just still set in the same galaxy or universe.

The sequel trilogy makes it 12 films. Also at one point Lucas also considered 2 other unrelated films, which would make 14.

Now we know Lucas only made the six and claims it was always darth vader's story,lol.