That's all been doable for a long time, using controlled breeding. We do it all the time with animals; look what we've done to dogs. The only difference genetic engineering brings is how quickly it can be done.

But that's eugenics, and it's been rejected as immoral by pretty much everyone. A big part of the problem, I think, is that a custom-engineered child is a lot more expensive to create than a natural random-chance child, and therefore eugenics only produces super-humans for the rich and powerful, who will become even more rich and powerful by breeding themselves into master race that enslaves everyone else.

Eugenics can't upgrade all of humanity directly because natural breeding, being cheaper, is also much more common. So the vast majority of inferior humans will always outnumber the eugenics-produced super-humans. That's where the enslavement comes in; the super-humans will have to use their inherited wealth and power to make sure they retain control because they can't out-breed everyone else.

The other possibility, and the only way the super-humans can replace the normals, is to kill off all of the normals either directly or by making them infertile. That's even worse than enslavement.

No matter how you look at it, eugenics has a bad outcome if it's not available to everyone at the same time. And if it was available to everyone, we wouldn't call it eugenics. We'd call it 'medicine', 'vaccination', 'pre- and post-natal care', and 'preventative care'.