Nice logic, if you can put it over on someone.
Well let's change the wording a little.
"You’re starting from an assumption - the existence of God, then claiming that based on that assumption, that the existence of God is true."
You are absolutely correct, the assumption does not make the conclusion true. Atheists agree that the lack of evidence that God exists, does not prove that God exists.
Nope, we don’t start from an assumption of a Creator,
but, we don’t automatically exclude the possibility then try to make all theories fit it, like the “yo yo universe” theory proposed to exclude the evidence of a beginning of the universe.
Atheists limit their discovery to the material in order to avoid the consequences of the possibility of a Creator.