Case in point, by having Ripley be a woman, there is an additional layer of depth in Aliens as to why Ripley's warnings of just how dangerous the creatures are mostly ignored by Burke/whoever it was, it's been a while since I've seen it.

That's not saying it wouldn't have worked with Ripley being a man, it would just be a slightly different story, because it would lack many subliminal themes of patriarchy, sexism, female hysteria, etc that having a woman as the protagonist allowed the story to more fully explore.

That said, there is a place for both gendered writing and genderless writing. It's all about the story you want to tell. Besides, without the concept or idea to try genderless writing, we may never have gotten Sigourney Weaver as Ripley, and that would have sucked.