Greed, lust, power, hate... These are just a few of the common themes of story telling. Why are they such common themes? Because these are the things that we, as human beings, witness and experience on a daily basis. When a reader can identify with what you are writing, you will make more of an impact.
This is also true in science fiction and fantasy. It doesn't matter how fantastic the setting is or how complicated you've made those monsters, if you don't have a plot that speaks to the reader on a personal level, then you don't have much of a story.
Ask yourself one question: Are you more concerned with the setting or the plot? If you are spending more time creating star maps and thinking up of more monsters for your protagonist to fight instead of focusing on the development of the story, then you might need to make a new outline. Details are good, but a plot that the common human being can identify with is even better.
Peace and happy writing!