Isn't 'natural birth is better than editting genes' kinda weird?

I like Man of Steel, but one thing's been bothering me.

If Superman/Kal-El is better then Zod because Superman was born naturally, and Zod's genes were altered, then why did Kryptonians have their babies all naturally born?

There's a movie Gattaca, I know this movie isn't about "natural born is better", I know this movie is about "You could overcome your fate", "Genes don't decide your fate", "You could achieve your dream, even if other people say you can't" but you know? If Vincent could have overcome his genes, why did so many people in a movie make their babies better genes?