CFC’s are great at coolimg things as long as you do not care about having an ozone layer.
They’re even fine if you care about the ozone layer so long as you never ever let any leak. Until the coolant leaks the CFCs are cycling in a closed system in which they can’t do any damage. The problem is that “not letting any leak” is harder than it sounds, and the newer coolants just don’t do the job as well.
It’s like how asbestos tiles are fine until they get damaged, and then they fuck the lungs of anyone unfortunate enough to breathe in a tiny bit of it.
It was never soundly debunked in theory. We are animals and like all animals our offspring inherit traits from us. Hypothetically if you could agree on what “good traits” looks like you could selectively breed people based on those traits and get people who are more likely than average to have those traits. Keep doing it for generations upon generations and you’d get people optimized for those traits. Even without knowing what gene or genes are responsible.
The problem is that we’re notoriously bad at deciding what is and is not in the set of “good traits” and tend to pick stupid shit like “being Aryan/white.” Also forced/restricted breeding is unethical at best, and fucking monstrous on average. It’s one of those things that goes in the bin of “it would probably work, but if we start doing it we’ve already become the villains”.