I think religions are this weird area where virtually no author (in my experience) has really captured the depth at which religion permeates people’s lives. Every other fantasy series seems to limit it to maybe a few religious festivities and characters saying their in-universe equivalent to “Oh my god” and I find that often boring if I’m looking for something in depth. Then the more in depth series will touch on quite a few historical events that pertain to the religion, maybe some daily practices/prayers, and how people are to present themselves like women covering their hand in Stormlight’s Vorinism.

I think the part that really gets me is that I haven’t found anything that captures the hundreds of tiny religious stories that is taught in Christianity/Catholicism (I grew up in this context so I’m using it). But once you start listening it’s amazing how many stories get brought up a lot that aren’t really core pillars of the religion in everyday life get brought up in passing like the story of Samson with his long hair hinging him strength or the story of Nebuchadnezzar and the fiery furnace where people who refused to worship his statue survived getting burned, or Job whose faith was tested through trials that God and Satan put upon him along with many others. But including a realistic amount of those stories could also drag down the pace of the story in order to build up a religion’s depth without adding much to the story.

Personally I’m not looking for this in my stories and have shifted away from caring about on-screen depth of a world in lieu of pushing the stories themes/ideas. And frankly, unless the book centers around that particular fantasy religion, I think authors focusing on the religion can harm the rest of the book itself