Hating children, as you put it, is not some harmless personality quirk. It reflects a profound lack of empathy and, in more extreme cases, can be associated with antisocial or even sadistic traits.
Unfortunately, your conclusion doesn't follow. The people most willing to have children are not necessarily the people best suited to raising them. Individuals with unresolved trauma, narcissistic tendencies, or even openly negative attitudes toward children often go ahead and become parents anyway. Children can provide a captive audience, a source of validation, control, or an outlet for dysfunctional behaviour.
So I'm sorry to burst your revelation, but both your old assumption and your new one are wrong. People with unresolved trauma have children. People who dislike or even hate children have children. In many cases, they are precisely the ones who don't stop to question whether they should. Meanwhile, the more self-aware, balanced, and conscientious people are often the ones who hesitate, overthink, or decide against parenthood altogether.