Hmmm good point. But I think the eugenics of the time was also based on class, ethnicity, and personal characteristics:

In the United States, “unfit” races have historically included minorities such as immigrants and African Americans, people with mental and physical disabilities, people in poverty, institutionalized people, and/or people convicted of crimes. Eugenics sought to eliminate these people, such that their “undesirable traits and behaviors” would be effectively weeded out of the human population over time.

https://en.wikipedia.org/wiki/Race_suicide

Note the 1903 illustration on that page “Concerning Race Suicide”. Everybody seems to be of European descent, but the wealthier people on one side have no children but the people on the other side – who seem to be coded as lower-class recent immigrants – have many chidren. I think that is being presented as a bad thing, though everybody seems to be happy and well-fed (if a bit crowded).