"When it works perfectly."
The presumption it ever well is a text book case of hubris. There is something very interesting about technology nerds are their illusions of control.
Gene editting is "easy", understanding the impact of the practice is obviously the barrier. Its obvious, even to the lamen, that the panasea of mapping the genome and editing genes is but a pipe dream. I remember when mapping the genenome was going to cure cancer, people spoke of it as if it were a sure thing. Then they completed it and it turns out that the genome isn't a "map" of anything. Its more like a puzzle of infinite complexity where every newly fit piece reveals a dozen more pieces that didnt exist before.
"What happens when it works perfectly?"
Who knows, but if we are talking hypotheticals here, why dont we just start making stuff up like we did when the mapping of the genome was but speck on the scientific horizon.