Oh yummy! My favourite!

But great seer Boz! This bean is not a gummi creature at all!

[...] I think you could very reasonably create a society that doesn't fall back to gods, spirits or demons to explain their own world.

I think an interesting spin in world-building would be to make civilizations more comfortable with the unknown. Yes, they might have significantly less knowledge about the inner workings of the world than we do, but if people are willing to admit that to themselves, [...]

I think the "need" for religion often comes from the fact that humans aren't comfortable with lacking answers. Being comfortable with "I don't know" is a big part of the scientific mindset, and that, relatively spraking, is a pretty modern doctrine.

Paraphrasing from one my favourite christmas story, Hogfather:
"So if we hadn't saved the hogfather, would the sun truly not rise tomorrow?"
"No, it would not."
"So what would happen instead?"
"We would make line of sight with a flamming ball of gas in the sky as it passes the horizon."