You raise some excellent points about what God would do according to scriptures but I was after a more generic answer since this was directed at atheists ho do not believe in scriptures.
This is an exercise in logic.
So,
if God exists we can know certain things about how God operates, or should I say how God does not operate.
Is there any evidence that God has communicated directly to everyone?
Is there is any evidence that God has proven that He exists to everyone?
No, there is no evidence that shows that either one of those has ever occurred.
All we have to do is ask people if God has communicated to them directly in order to know if this is the case.
If people say that God has not communicated to them then we can logically deduce that
if God exists God would not communicate directly to everyone...
Since atheists exist we can logically deduce that God has not proven that He exists to everyone.
That means that
if God existed God would not prove that He exists to everyone.