All one can respond with is the "Free Will" argument. We are creatures created with a freedom to choose, to believe, or not.
My own brother, an atheist, put it succinctly. "If there is an all-powerful God, why does he not simply appear to us and prove it once and for all? Then, I'd worship."
The answer isn't complicated. If a giant face suddenly appeared in the sky, and boomed out "I am God/Allah! I have might powers! Worship me!!" And day turns to night, the moon turns purple, and it rains diamonds, or clams; whatever. Every TV station and radio has the same image and voice.
The power is obvious. The existence cannot be denied.
At that point, humanity would be instantly turned into robotic drones and forced to worship, as any rational being on earth could not at that point deny His existence, and would fear his wrath. Only a lunatic would do so, given the evidence.
But God does not want robotic, worshiping drones. He wants us (on our own) to turn from evil, and seek Him with humility and repentence, based upon faith, not force.