Oh, I agree, there’s definitely a lot of genre overlap with SW. And much of sci-fi does defy any single label. However, since science fiction has the word “science” in it I personally tend to equate it to the term speculative fiction which implies at least a certain degree of what’s being shown will be plausible one day. SW doesn’t really fit into that genre, nor does the Barsoom stories. Now, obviously there’s a lot that isn’t realistic in much of sci-fi, with Star Trek being a very good example. But as I said in my Addendum #2 the premise is one of exploration and there’s always some attempts at keeping the technology somewhat within the realm of possibility, except for when it prevents the stories from being told (like how there is no time-dilation in warp-travel, etc.). Plus, much of the pseudo-science, like telepathy, was believed at the time it was made to be real science, so it was at least an attempt at science fiction.
Besides, I’m not really denying that SW has elements of sci-fi in it, like it does with so many other genre as well, but “Star Wars is surrealism, sci-fi, a western, a samurai film, a space-opera, a fairy-tale, and so forth” doesn’t make for a very eye-catching title. And I do think that it is primarily a fantasy/fairy-tale at it’s core, while the rest are mostly aesthetic influences.
I also think it’s interesting how the sci-fi genre originated in a time when space travel seemed so absurd to people that it might as well have been fantasy, so weather you were reading Burroughs, Doc Smith, Wells or even Robert E. Howard, it was all classified as “science fantasy.” Then after the first satellite, the first man in space and finally the moon-landing in the 50’s & 60’s then suddenly the absurdity of some of the old science fantasy stories didn’t seem all that crazy anymore, and people started to differentiate authors like H.G. Wells from Edgar Rice Burroughs, with the former retaining the science fiction label while the latter gradually being reclassified more and more as fantasy (or Sword & Planet to be more specific).
Well, there is what things ARE called and there is what they should be called. What we call Science Fiction should really be Technology Fiction. Think about it, no matter how much science, the stories all deal with some level of technology. Sometimes, like Steampunk, it is backwards extrapolation of what could have been in a past time. But always technology. Similarly Fantasy is really Magical Fiction. All the stories deal with magic in some way, from magic creatures, to wizards and talismans.
But we are kind of stuck with how the genre names have come down to us and how they are used. Unfortunatley Speculative Fiction is the current umbrella term for all Science Fiction and Fantasy and a bit of Horror as well. Bookstores don’t use it, but writers, agents, and publishers do. And movies are never as divided as literature. Everything even remotely science fiction gets thrown under that label. I have seen some adoption of the term space fantasy, but that is usually just space opera rebranded. A lot of it is just semantics. The word science throws a lot of people off. Asimov usually populated his stories with scientists, but the plausibility of his stories was no better than Burroughs or Star Wars. Especially his Mule and Second Foundation and then the Robots he made responsible for those abilities. But being a scientists himself, he was always good at making his leaps sound logical and plausible even if they were not at all.