Boris Gudenuf
Deity
Following what they've said about the Ages, I could see the 2nd Age Crisis Period involving the rise of Enlightenment/secular thinking and the incipient Industrial Era to downgrade the importance of religion dramatically - an included Religious Crisis Period, so to speak.The challenge to implement this is that within the ~150 turns of the 2nd age, you need to have a full cycle of foundation, spread, competition, dominance, decline, crisis. I can see a religious-oriented crisis in the end of the 2nd age though that may wipe out or divide your religion. In the last age, there‘s possibly something else that takes over the main path for happiness - although religion might be possible to keep if you specifically choose so (e.g., a religious ideology) Yet, I think we were told that the main spot for religion is in the 2nd age.
That, in turn, would open up the Modern Age as an Age of decreased importance of established religion but increased importance of ideologies like Nationalism which invoke the same fervor that religion once did. That simplifies the models of religion and ideology considerably, but not too much for game purposes: basically, to get the same levels of Happiness and other bonuses you got from Religion, you have to start all over, or nearly all over, with Ideological/political conformity and Consumer Goods for population happiness.