What did that tell me? It told me I hadn't done much in the way of research as to what the market had been publishing. My story was a standard end of the world story, told from what I had hoped was a different enough perspective. I was so wrong. How many of you have tried to write the quintessential vampire story (and your initials are LKH or AR) and had the same thing happen? Or the perky young wizard battling evil? There is such a thing as market saturation and market timing, and it can kill the writing career of anyone not willing to look a bit further afield in what they want to write.
Almost everything has been done to death, many times over. Take zombie stories for instance. How many zombie short stories are rejected every day because it is the same tired theme over and over again. I recently had the opportunity to critique a zombie story told from a very unique point of view. When I picked myself up off of the floor after laughing myself out of my chair (I hit the ground hard, let me tell you!) I knew this writer had that special talent to take a trope and turn it inside out. I will post more about the story when it is published.
So, take these rejection letters to heart. Read up on your chosen genre. Try to think out of the box. You'll be a better writer for it. I know I will!