Western culture already has driven fertility rates well below replacement. Alongside that we also have skyrocketing obesity rates, skyrocketing rates of mental illness and drug dependence/abuse, plummeting testosterone levels, the end of the Flynn Effect, governmental approval ratings approaching zero, and more. Our culture, in its current form, is not even remotely close to sustainable.
There has to be some meet in the middle between "Follow the ancient holy book, or die!" and "Let's hedonize ourselves out of existence." As both those extremes mostly feel like two opposite ends of a horse-shoe, to me.