You have to believe one of two equally unlikely events: Either the complex web of life on Earth, including humans, evolved from the primeval ooze all on its own with no purpose, or no intelligent guidance, or there is an intelligence greater than our own behind it. You don't have to buy into the Christian or any other creation story to believe the latter option. Your statement that we can't come close to guessing what god is like is right on target. Yes, man has created religions to try to explain the inexplicable.
Most of us, down deep, are really agnostics. Some people say that they know that there is/is not a god. Some even say that they are sure they know about the unknowable. But, in the end, no one can prove that their belief is correct.
Which of the equally unlikely scenarios do you choose to believe? Life in all its complexity just happened by accident, or there is an intelligence behind it all? No one knows. We have beliefs, but none of them can be proven, including atheism.