It’s definitely possible to establish reasonable thresholds - you could draw parallels to abuse/neglect laws. There are things that many people may find grotesque and objectionable that aren’t considered abuse/neglect. There are definitely historical and modern examples of those laws being applied unfairly, particularly to the disadvantaged. Boundaries may flex across regions or cultures, But it’s fair to say society as a whole supports abuse/neglect laws, and that they’re generally beneficial for children.

I’d rather see better detection and genetic therapies, myself. Inform the parents and let them come to their own conclusion about whether or not to have children.

A perfectly reasonable take, but even that falls in-scope of eugenics.