If you consider stories set in the far future you don't have to consider the characters because the setting itself doesn't exist. You can't have a story set in the future that isn't F or SF.
I could just as easily argue that Star Trek wasn't science fiction because the science fictional devices it used were just in place to comment on the zeitgeist of the day and to drive it forward in a specific direction -- a morality play, if you will.
CS Lewis and Tolkien were not Fantasy writers they were Christian propagandists.
Labels are an inexact means of description they always narrow the essence of what they are applied to. This is why so-called mainstream writers who write stories that are on the face of it SF loudly disclaim the obvious.
The things authors think they are putting into their works are not always the things the readers take from it.