["How on earth is belief in God the default? Infants don't have a belief in God until they're taught to believe in God by their parents or someone else. Would you say that belief in pagan woodland spirits is the "default" as well?"]
Who told the parents and some else?
Infants don't know any better, and even if no one tells them they will come (later in life) to the conclusion that there is a creator if they search deep in reality.
Don't you see that most humanity has come the logical conclusion without God say anything.
You are the one in a fantasy world were there is no proof of no creator, if there is no creator there is no beginning in time.
Scientist and many philosophers agree time is finite and there was a beginning in time, meaning that after all there is a creator. Someone higher that ourselves, and this is just I of the reasons to believe. Why is there any doubt because you have not seen God? Of course you have because you are alive!!
You can also be taught not to believe. Is the world round ? sure it is. have you seen it? no. only in pictures.