I can remember this movie "Field Of Dreams", starring Kevin Costner, about someone who built a baseball stadium in the middle of his cornfield because he heard a voice saying "If you build it they will come." And when he built the field, the ghosts of star baseball players came and played on his field. It was a romantic notion, but uplifting in its way. I can't remember the movie clearly, but it seemed to be about reaching out in faith rather than letting yourself be trapped by dull reality. Okay, so it's not that simple, or we could all change things at will. But sometimes if you step out and try, it will lead somewhere.
I was almost jealous that I hadn't had that idea for a storyline. It works the same for writing. Fiction is fiction, and it may reflect wishful thinking; but if you write about what could be, sometimes other people might take up the idea. Harriet Beecher Stowe wrote "Uncle Tom's Cabin", and aroused considerable passion about the issue of slavery.
A British novel "Kes" described a day in the life of a boy who lived in a dysfunctional home, with a negligent mother and no father; and the way every thing that could go wrong, did so. The message, not so original but still true: it is wicked to bully younger children, like the older sibling did in "Kes".
The best approach to writing a novel, a poem, a film or anything is to write about what you feel strongly about. And if you say it, some others might hear it, agree, and be encouraged to hear their own thoughts expressed by someone else. You know you are not alone in thinking and feeling certain things when you hear someone else say the same thing. That is probably why there is a limitless market for songs about love, broken hearts, looking for love, and all that. People feel it so they get help from hearing someone else put it into words. Sometimes, obviously it can be a real 'duh' moment to hear a person stating the obvious and thinking it makes them clever and profound. But still, there is a time and place for saying it, or writing it, and seeing who else thinks the same.