I probably knew quite young religion was all a load of rubbish when I skipped RE at school. It was because Dad was Jewish mum was C of E so when I was asked at school what religion I said none! I have never, since then, heard a coherent argument for any religion, so I drifted along maybe agnostic? I read voraciously philosophy and psychology and still didn’t have a fixed position until I heard Ted Grant ( Militant) talk about the political development of religion that was an eye opener. Some years later I read The God Delusion and later God Is Not Great and finally the blindingly obvious became clear.
p.s. I was in a rock band pub about 2 years ago and a young guy had a Tshirt with F@@K all your gods spelt out - I thought it was brilliant it epitomised what I felt. I’m not sure I am brave enough to wear one but would love to !!