So would you say that a belief system is more correctly described as a narrative about how the universe came into being and eventually lead to exactly to where you are right at this very moment?

If so, then isn’t that narrative sort of a God-construct, because it explains who and why you are and why you do what you do? Because I would argue that this narrative then IS your God, as that is what created the world YOU live in, and determines everything that you do. You are therefore functionally behaving like a theist, whether or not you deny it makes no difference to me.

science is not a religion, because religion relies on belief. science relies on reproducible data.

Science is the belief in the scientific method as the best tool to determine the truth. And it could certainly be said to fit the definition of religion if you go by Cicero’s explanation of its etymology, which says that religiō comes from relegere: re (meaning “again”) + lego (meaning “read”), where lego is in the sense of “go over”, “choose”, or “consider carefully” — all of which are certainly required in order to correctly do science.