You are ignoring the externalities. We end up with an ignorant society that ultimately harms all of us. I hate to use a movie trope here, but we're barely a step above Idiocracy when it comes to the ability of the average American to function and make decisions. This ultimately becomes self destructive.

I went to a young earth creationist Christian school and it messed me up. Most of us had a hard time adjusting to life outside the Evangelical Christian bubble. It's really hard to connect to others when your identity is tied up in believing a lot of outlandish things and it's hard to love yourself because you're given a long list of crazy rules to follow. I was told that kissing someone before I was married would taint my soul and whoever I married would be disgusted by me if I did so. Most people I've kept in touch with regret going to that school and every queer person I know has been absolutely traumatized by the experience. I'm happy, and by your criteria, a good member of society but that was despite my school. It took a lot of therapy, personal growth, and finding a community of people who actually care about me to be happy.