Who does the food pyramid not work for?

Please clarify: There are different food pyramids, so which is best for you depends on many factors which makes it impossible to address your question. There is, for example a 'paleo' food pyramid compared to the usda pyramid and they are very different, based on different hypotheses about which foods are healthiest. Some is based on science, and some on political biases.

No one: The food pyramid is not a healthy way to eat. Look at the many resources that show you how to eat with a paleo or primal approach to your diet. Keep in mind that the only thing your body needs carbohydrates for is fuel for your metabolism. And the average person only needs about 100 grams per day.