“we all, surely, want children with good genes[…]”
What are “good genes”? I can understand some obvious cases, such as avoiding genetic diseases, but trying to assign value to some indifferent assembly of molecules is another case of senseless anthropomorphism.
What is more, genetics is a weird field, with interactions between genes, epigenetics and mutations rendering any attempt at predicting outcomes pretty much moot, beyond some very basic and targeted aspects.
You can select embryos based on the coding for one protein. It becomes pretty much impossible when you try to give more complex conditions. Skin colour, eye colour, hair colour, just to take some obvious examples stem from so many genes that only an idiot can think it would be able to precisely select the traits they want.
“There are better people, and there are lesser people”
Based on what? Without even going into the ethical debate, a muscular meathead has a certain value in certain circumstances, but a smaller individual will have a better outcome in some other circumstances.