Stories don't need to change the world to have value. They can exist to entertain or make someone feel warm inside. It can mean a lot to just a few people not to a very wide audience. It can also exist just because you want to. And that alone is  a good reason to write. It doesn't make your story less valuable than others. 

We all love a book that makes our heart sing, that questions how we view the world, or characters who'll haunt us for years afterwards. But sometimes, all we need is just an uncomplicated page-turner to take us to wherever we're not.

A story can not change the world as a whole, but change a person's whole world. More often than not books without an obvious "agenda" or "platform" still always create meaning, even if it's only escapism. People find inspiration and importance in a number of pursuits, not just the world changing ones. 

Value your words, raise it.