Decent surgical knowledge took a millenium or two to develop, accelerating in the past two centuries.
Equivalent genetic knowledge is in its infancy. Sometimes miraculous results can be had, even today, tinkering around the edges. But major messing with the germline, aside from selective breeding, which has its own ethical issues, is going to produce many failures.
‘Someone’ has the goal of changing humanity from ‘made in God’s image’ to made in ‘someone else’s image’.
And the failures probably won’t be known until after years or decades of use of a presumed safe technology.