Kinda! I wouldn’t say that it is exactly science fiction since our modern understanding of the scientific method didn’t really exist back then, but it’s fiction using extrapolations of what might be possible based upon the natural rules of the world. Those extrapolations are used to justify and explain the things that would otherwise be impossible, which is the core of what science fiction is to me. It probably doesn’t vibe like modern sci-fi, but science fiction is not based on vibes.
Like, don’t get me wrong, I fucking love 50s and 60s sci-fi. I read Rendezvous with Rama (EDIT: 70s, not 60s! I’m surprised, I thought Rama came out before 2001) when I was 8 and the novelization of 2001 right afterwards and that had a tremendous impact on my life. I just don’t think Arthur C. Clarke or Heinlein or Asimov created science fiction. They pioneered new subgenres and ideas that have been hugely influential for everything that came afterwards.
Like, I think your conception of science fiction is very specific, and that’s fine. I’m guessing you really love sci-fi and feel strongly about it, and you think this shit is just weird af. The general consensus is that Frankenstein is the first novel to really be considered science fiction and not, say, proto sci-fi, and there are plenty of reasons why people think that which you can read about if you care to. I personally feel like Frankenstein is science fiction because it explicitly uses a contemporary understanding of science and the modern scientific method to tell a story about something that had previously been entirely supernatural—the creation of new life. You have your reasons for disagreeing with that. I don’t know what those are, but you’ve got them and clearly feel pretty strongly about them.