Are we really already far enough along in understanding genetics to do a better job than the process of natural selection? Given, we've been manipulating it wel

Are we really already far enough along in understanding genetics to do a better job than the process of natural selection? Given, we've been manipulating it well for over a century now, which makes me wonder what percentage of the global population would not have survived to reproduce even two centuries ago? Modern Medicinal science is amazing, but in this field I could easily imagine a scifi future where humans are no longer able to naturally reproduce. Is there any concern with this in the scientific community or is this just my writer's imagination on an unfounded basis?