All possible explanations for existence have a 'well okay, but what created that' issue. Whether you start with a God, or with a quantum fluctuation, one is left asking - okay well what created the God, or what created the void in which quantum mechanics (and who created such a system to begin with) burst forth. There is no answer to these questions, because regardless of the story - it always ends (or in this case, begins) in the same very uncompelling way - 'Well it just always was.'

In any case, the mystical and physical are not fixed. Imagine explaining the consequences of relativity to a skeptical individual of times past. Think of his response to the notion that time itself is a variable and can move at different rates for different people in different circumstances. It sounds like absurd mystical sci-FI nonsense. Except it's real, so now has been promoted from the mystical to the physical.

So what a skeptic of today would label "mystical" will almost certainly change over the centuries and millennia yet to come. Scarcely more than a century ago, state of the art transport was a horse, computers did not exist, quantum physics did not exist, relativity did not exist, human flight was widely believed to be impossible, and so on endlessly. It seems unlikely in just a century that we've even scratched the surface of knowledge yet to come, let alone meaningfully penetrated into it.