I like sci-fi elements in D&D. An alien being that crashed and became the object of worship by an isolated people/cult. A spaceship buried in ice that acts as a dungeon. Fallen high-tech civilizations with rusting, jungle-covered ruins and dangerous inhabitants. The occasional ancient artifact or "golem" (robot). Psionic four-armed apes that worship Great Cthulhu and wait for the stars to become right.
I'll even go farther, for some campaigns. Flying airships, projectile weapons, and ray guns. Barsoom. Blackmoor. Et cetera.
I love Tolkien-style fantasy. I also love weird tales, swords and sorcery, swords and planet, and that early period when fantasy was still considered part of the science fiction genre, and there was a lot of crossover influence. These elements were present in D&D from the beginning.
Years ago, I used to think that sci-fi elements had no place in D&D. My tastes have changed, however.