The movie was based on the (indisputable?) fact that intelligence is heritable- but not Eugenics, which takes that a step further and advocates for people deciding which other people are inferior and superior and organizing society around that. One could argue that the movie tries to make a case for eugenics, but it didn’t directly do so. I think the movie could also be seen as looking at culture instead of genetics, and also assuming that is passed down from parents.
I agree that it does wrongly depict poverty as a major indicator of intelligence.