Everything that emerges from our amazingly fertile imaginations springs from our experience. This forms our ability to imagine such things, not visa versa. But now we can imagine these wonders with ease. Experience is primary and we cannot imagine outside of human capacity. With everything in the universe expanding away from the rest, every point appears to be its center. Outside of the universe nothing exists; there is no "there" there. (Even parallel universes are just imagined copies of this one.) Like a gas filling a vacuum; the gas cannot fill a space that does not already exist. So too the universe cannot be bigger than itself and the human cannot imagine beyond its boundary.
Humans have the amazing capacity to extend our senses and find new treasure, but we cannot create prima materia. In other words a mortal creature cannot create something outside the created order, only God can do that. So how could we create the concept of a God that is greater than that created order? This is like the child saying it imagined its mother. Cute, but impossible. The only way we can think of a universal God is if somehow the reality emerged prior to our imagining. The idea of a creator-of-all could not be thought of unless it emerged as a discovery.
Whether we chose to believe in the Great Mother or dismiss Her as a fantasy is up to us. Nevertheless, as Carl Jung says, "Invoked or not invoked, God is present."