That's sort of the point of fiction, though, isn't it? Sure, a more complex fiction might be more rewarding, but simple ideals can also be very satisfying and can be grounding too.
It's pretty much impossible to have that. You'll always have the author's worldview shaping the fictional world.
The common cold thing is a direct reference to what happened to European explorers when they first encountered syphilis in North America.
I don't expect, and don't think most people expect, for authors to not have their storytelling shaped by their views. That would be impossible. But it's not impossible for them to refrain from derailing the story just to lecture the audience on morality.