To argue that the existence of God does not solve the mystery of existence.
Ya gotta solve it for yourself. Or not. I kinda prefer not. I like the definition of "mystery" (in the theological use) as:
That about which we can know more, but never completely.
The mystery of existence… We could have existence and no mystery. Or no mystery and no existence. Or existence and the mystery of it. If you were in charge which would you choose?
If you solve it, it's not a mystery anymore. Would you prefer someone told you the solution when you were a sophomore?
Or, how about this mystery: We exists AND we know we exist in this material finite cosmos (and that we will cease to so exist). Now what's the purpose of THAT?
You're interested in these kind of questions, they matter, have meaning to you. Why?
To argue that the existence of God…
To argue the existence of anything we'd have to have a bare minimum of agreement on what it is.
How would you define God?