It’s not completely wrong, especially since humans long left the checks and balances of natural selection. The thing that was ultimately bad about eugenics was how the Nazis enforced this onto the general public through selective breeding programs and viewing everyone else as genetically inferior. But saying that genetics and hereditary traits aren’t a thing is just as anti-scientific. In case of the movie it was not just about genetics though, especially since intelligence is just partially based on genetics. It was also about smart people not having kids and consequently failing to do better parenting than the morons that decided to have kids. Some people may escape the cycle of a family that is not good for them, but a lot of them will just carry on the same behavior that they learned from their parents.