That only applies to more trivial things, like hair colour, and iQ scores, but when it comes to health fixing, no one would refuse correcting health issues. As for playing God, that only applies if exists, and if He does exist, i would argue that he gave us the knowledge to be able to do these things in the same way He gave us the ability to bring more human beings into the world. therefore the issue is not whether its unethical or not, but on whether it is beneficial or harmful. Is it harmful? you can agree that its not. Is it useful, fuck yes to save many babies from future harmful mutations.