That's why it's called faith. We know it's unprovable by materialist standards. I can't speak for others, but I have learned to trust through 1. reading the scriptures and 2. revelations received during meditation and prayer. These are experiential, and cannot be replicated, since God is part of the consciousness of each unique individual. There is no substitute for looking within your own mind for answers instead of demanding them from others. If you have already determined the answers, no amount of proof will satisfy you, nor will you hear the "still, small voice."
Then why would someone try to point to a supposed logical demand that the apparent complexity of the universe demands a creator? Why the reliance on materialist standards of proof to demonstrate a designer of all that there is?