This is a matter of culture. Aquinas is not wrong, but there are other ways of viewing the question.
The assumptions that would support embryo selection include 1) morally speaking, life begins later than the first few cell divisions, and 2) parents know the traits that will make a better, happier life for their child.
I'm not touching assumption #1 on this board except to say that opinions differ, but #2 ties in directly to hothousing vs afterschooling and all the parenting issues we deal with as adults who love unusual children.
I do know parents who want their children to succeed to get them boasting points, but I also know parents who push their kids now out of love and hope they will be happier for it later. I am not going to raise 100 kids - just one or two - so out of love, I'd want them to have the best set of traits I can give them. Given the choice, would I have chosen for my daughter to have a chronic disease? This is a matter of her happiness. Would I choose for her to have less than average intelligence? Probably not. On this board, we see a lot of downsides to high intelligence, and have to argue every single day that high IQ does not make you a better or happier person. Some of that is pushback against resentment from others, though. What I understand of Chinese attitude says that intelligence is a tool that a person uses to get to success, which is what ultimately matters; overall they don't respect or disparage someone for their ability, but for their achievements. Why would I want my kids to be born with inferior tools? That would make their lives harder, and as a loving parent I only want the best for them.
Personally I think that a strong population has a wide variety of traits, and I'm a poor predictor of what makes my kids happy, so this isn't something I would choose. I do understand why others might, though.
