There is no moral problem repairing genetic disorders. That is more moral to repair a defective embryo's bad gene than the prenatal genetic testing we do that leads to 95% of those with Down Syndrome being aborted.
What gets interested is when we move from "ensure your kid and no descendants carry the trait for Tay Sachs or hemophilia" and into improvement. Given that 1% of kids in the developed world are made via in vitro fertilization, replacing a few genes with those associated with higher intelligence, better endurance and longevity is easy for those cases. And the costs associated with it do limit it to the upper middle class.
People are a mix of nature and nurture, but genetic engineering is only affordable to those with the good nurturing environment. So they get the best environment (on average) and now even better genes.
Genetic engineering won't guarantee beautiful, brilliant, happy people. We don't yet know enough about the interplay of genes and proteins to do that. It could lead to a caste where the elite has an extra thumb on the scale academically and physically, where merit is now more strongly correlated with genetics that reinforces over time. (only 10% of millionaires inherited their wealth, 90% are first generation, because many rich don't retain it when the business is passed down - with extra IQ points and education to match it, that might shift)
In the short term, I see much more genetic testing of embryos when women are pregnant. They added more traits they could test for between my pregnancies. And now they can test based on fetal DNA in the mother's blood, so they can test in the first trimester - when most are much more willing to abort a problematic fetus. So we'll see more weeding out of undesirables.
If enhancements ARE available, they'll go to the richest first like all technology, and it would reinforce the class system we're developing now.
The only caveat is that I don't think that class system is going to arise from genetic engineering. It is here because of assortive mating, because women who went to college only marry guys who went to college, versus guy who starts a big company marrying his high school educated secretary or the girl next door before hitting it big.