It would suck! Everyone will choose the same traits for their children, and humanity will end up being a heap of inbred people. Besides, how can we know what are the most adaptive traits? For instance, a negrito could be the best genotype for times of hunger. Likewise, a tall, slender, and dark African is best suited for the tropics than a bulky, red-haired viking, whereas the opposite is true for the North Pole. Have you seen the movie "Gattaca"? It's quite illustrative.