So people with sickle cell anemia, trey sacks, cystic fibrosis can have children that are theirs without passing on the gene for those traits.
Selfish perhaps, with so many children who need adoption; but “hellish”?
Actually this doesn’t help with any of those diseases. Those are all due to defects in the main, nuclear DNA, that comes from both parents. Mitochondrial DNA is outside cell nuclei, in the mitochondria, and is passed down only maternally. This process substitutes normal, healthy mitochondria from a donor egg, for the mother’s genetically defective mitochondria.