> The problem with those high-fertility groups is that they usually come with a lot of baggage - specifically they require belief in the made-up nonsense that tends to fade away as the demographic shift advances. So, they may maintain higher fertility rates, but I'd wager more and more of their kids will break away from a religion/belief system that appears increasingly absurd and stifling as the rest of the world moves on.

Honestly... I've simply not seen this. There are many religious people in prominent positions, you just don't know about it. In my fairly traditional catholic parish, we have families where mom and dad are catholic, their five kids are catholic, and their 40 + grandchildren are as well (some are now adults and having kids of their own). And all successful, doctors, nurses, engineers, etc. The idea that religious == stupid or baggage or whatever is simply at odds with history. You're conflating the Duggars with otherwise normal people that just have different views.