Bingowings said:

We will have to agree to disagree.

Yes, we can agree to disagree. None of the items in your list strike me as fundamental to the story, which is the development of Luke. Han's redemption is a great subplot. None of the other characters develop or change; they are all there in support of Luke's development.

As far as the "unusual-ness" of the worlds, I think Lucas did what he could while still making it look believable. I think he wanted to take the viewer as far away as he could, and make the viewer really believe he was there. As technology improved, he made the worlds increasingly strange while retaining the impact of realism. The cantina, for its time, was extremely bizarre while still being convincing. Star Trek, by contrast, didn't worry about making its worlds convincing... and many of its stories were centered around moral quandries.