I see what your’re saying, and I agree that it’s probably the only practical way of dealing with these genres. I personally find reducing stories to just technology and magic a bit too rigid as these are just tools used by characters in stories, and ultimately stories are about people and themes. Although it’s probably not all that practical, I personally would like for these to define genres. But technology and magic is probably the simplest way to separate genres as it at least gives people a sense of the aesthetic/atmosphere of the book or movie they are about to read/watch.
It does still annoy me though, since I feel that spaceships doesn’t necessarily mean sci-fi unless it serves a theme of science, and magic doesn’t always denote fantasy, especially when it’s not done in a mythological way.
Even though Asimov’s books include a lot of things that probably won’t/can’t happen (though this has been said of sci-fi many times until it actually does happen), yet his ideas are as I’ve mentioned before with Star Trek, rooted in themes of human exploration/development. The society depicted in the Foundation books may seem exaggerated and fantasy-like, but the idea of storing all human knowledge to minimize the duration of an inevitable age of barbarism predicted through an a scientific method that can simulate the most likely outcomes of predictable human behaviour, is at it’s core a very science-based concept. We can argue about exactly how possible this is, though computers are only now starting to be able to do large-scale simulations, so who knows. Asimov made it a math-like process, but he wrote it in a time when computers were just starting to become somewhat useful. The idea however, is science-rooted. And it’s from the 50’s, so it still has that veneer of Flash Gordon and Buck Rogers, but the ideas are all based on intellectual concepts, and the human stories are only second priority, almost treated as a mere necessity as civilizations do of course center around people. What Asimov is really interested in though is civilization as an concept.
Fantasy on the other hand, at least when done properly, I would say is more rooted in themes of mythology and fairy tales. Unfortunately, a lot of modern fantasy is written from a sci-fi viewpoint were magic is basically a metaphysical science with specific rules to be obeyed. Now this is an interesting concept, but it really should get it’s own sub-label (which it kind of already has in Hard Magic) as it has little to do with true fantasy. Classical fantasy, like Narnia or The Wizard of Oz are, like mythology, purely symbolic affairs. They are not meant to be made sense of through literal interpretations. Even when fantasy creates an elaborate lore, like Lord of the Rings, you can rarely figure out how exactly the magic works or where exactly the stories take place. People have tried to superimpose Middle-Earth over mas of Europe, but like Erewhon and Newhon, it’s a nowhere and a nowhen. Likewise with Star Wars, you can find many videos online where fans speculate whether the SW-galaxy is supposed to exist in our universe/dimension, but like those who tried to equate the Shire with England and Rohan with Norway, I feel they are missing the point.
Of course where things get really complicated is when you star to analyse writers like Robert E. Howard who literally superimposed his own Hyborean age map over a map of Europe and created his own fictional pre-historic timeline for the earth. Is that fantasy? Sci-fi? Maybe the old term science fantasy still applies to his work in particular. The again there’s not much science in his writing. Maybe speculative fantasy should be a thing.
So, all my ramblings aside (I’m probably starting to sound like a broken record at this point), most people will most likely continue to label anything with spaceships as sci-fi and anything with wizards as fantasy, so all we can really do is provide sub-genres for those of us who do care about the minutiae of fiction. But I find it especially fun to challenge the genre definitions of Star Wars in particular as the very first movie basically has a wizard in a spaceship.