There's very much an ethical problem here. Sure, it's fairly clear-cut with some debilitating genetic issues. But there's a point at which you're veering into eugenics, and that's sooner than people think.

Take children who are deaf due to a genetic defect. I'm sure most parents imagine being deaf a terrible lot in life that they'd like to spare their kids from.

Then listen to actual members of the deaf community. They're proud of their identity, they have their own language, and they're terrified of the prospect of being essentially eliminated in just a few generations by well-meaning folks that can't imagine a happy life as a deaf person.

What if we discover a few years from now that there are genetic markers for being queer? What if we can genetically engineer people to be thinner, more muscular, have a more attractive bone structure, lighter skin? Those are all things that offer an objectively more comfortable life, which I'm sure many parents would want for their kids without much thought given to what the societal implications are.

And what if this technology becomes available to a charismatic cult leader, a narcissistic tech CEO, a fascist regime?

Such technology doesn't just fix genetic diseases. In a hierarchical global society that measures people's worth by their body rather than their character, it eliminates human diversity.