There are plenty of skilled writers who have already entered the contest and written some interesting things under 300 words. Not only that, but I think it's the sign of a strong writer to be able to compose something interesting and meaningful within constraints like this. It tests your abilities, and forces you to be really creative to fit something into those parameters. I think that you should try your own hand at this contest. If you don't enter, you can't win, and you're not testing your limits to see what you're really capable of. (Just as a comparison, think of chefs competing in Iron Chef or Chopped. They have to be extremely good to come up with something inside the existing rules of the competition.)