Science Fiction and Speculative Fiction are two of the most subjective genres in writing. This will tend to blur their definitions. Speculation is also a natural component of science. So, writers will always be tempted to cross these genres and they work well together. I do it all the time. Is there such a genre as Speculative Science Fiction? It seems logical to me.
I've always liked the work of Gene Rodenberry. He was very imaginative and wrote stories that were fairly close to being scientifically correct. But he did toss in some Hollywood fantasy here and there. It sales well. However, the last major project he was involved in, "Final Conflict Earth," was taken over by another Rodenberry (I guess his sun) and messed up the story. He killed off a main human character and changed the aliens.
George Lucas is good. However, he seemed to be stuck on writing stories about war. If he were not, I feel he would have written a post war follow up series to "Star Wars." He still had two very good living human characters to work with, as well as others. And, some of the characters that were killed off were able to still pop in now and then.
Isaac Asimov is a thinking man's Sci-Fi writer. He writes some amazing stuff and understands science.
Well, time to fix dinner.
Light
Science, Science Fiction/Fantasy, Metaphysical