I have to disagree here. The abstractness of Space Mountain is part of it's beauty. Not every ride needs a detailed story. Space Mountain is more experiential than it is literal- and that's its biggest strength. It is what you want it to be.
95% of the people who ride Disney rides don't listen to the dialogue, or pay attention to the story. I bet most who ride splash don't have any idea what's actually happening, but it's a fun ride with great music, so it works.
The Matterhorn and BTMRR are both fairly abstract experiences as well- it's virtually impossible to tell a good story with a roller coaster (which is part of why I worry about the Incredicoaster), and I'm glad they didn't try to shoehorn more into Space Mountain.