Space Mountain to me, works because it doesn't *need* to have a grand or overly complicated story. It's just going out on a patrol into the reaches of the galaxy. Could they add more scenic pieces, to enhance the feeling of travelling through space and seeing stuff like asteroids, planets in the distance, and other ships as we travel? Yes. But wanting a grand story for Space Mountain doesn't make sense for me at all.
Disneyland, ain't the Paris Space Mountain.