Having established (I hope) that stories are about something, which we’ll call its ‘theme’ for want of a better word, there is another element that’s central to every story.
When the first humans sat around the fire and told each other stories, they were about the tribe’s exploits, the gods and the spirits and the animals and everything else under the sun, but really they were telling each other about themselves. Humans have always put themselves at the centre: Jerusalem (or Delphi or Atlantis) is the centre of not just the world, but the Universe. (I’ve just looked up “centre of the earth” on Wikipedia for a few other examples only to discover that the Centre of the Earth is less than a tenth of a mile from where I’m sitting now!!!) People didn’t used to believe that the Sun went around the Earth, what they really believed was that the sun went around them, personally.
Stories have this same ego-centric aspect: they may be about gods and animals, but the gods and animals are really different aspects of people. To tell a tale about Loki or about the fox, is really to tell a tale about any trickster character.
Thus stories are all about the human condition.
They must be for they are mechanisms to pass on knowledge and culture; that knowledge and culture must be applicable to the story’s audience. You can’t really tell stories about anything else. What’s a story about the orbit of Proxima Centauri to me? It needs people (or people dressed as aliens) in order to dramatise it. As soon as the story is populated, then any number of interesting things about Proxima Centauri can appear because these facts are told in relation to human experience.
Stories must have at least one person (or person dressed up as a talking car or an insect or whatever) in them in order to act as the focus of the human interest.
Thus: stories are about the people.