They became fools

For since the creation of the world His invisible attributes are clearly seen, being understood by the things that are made, even His eternal power and Godhead, so that they are without excuse, because, although they knew God, they did not glorify Him as God, nor were thankful, but became futile in their thoughts, and their foolish hearts were darkened. Professing to be wise, they became fools, - Romans 1.20-22

There can be no doubt that we live in a day of marvels we could never have imagines. Man is capable of amazing things. Who would have guessed we would be carrying computers in our pockets or that our cars would drive themselves or that we could use a printer to print food?

Man thinks he is pretty smart. Man thinks he has outgrown God.

There is this, for example:

God is dead. God remains dead. And we have killed him. How shall we comfort ourselves, the murderers of all murderers? What was holiest and mightiest of all that the world has yet owned has bled to death under our knives: who will wipe this blood off us? What water is there for us to clean ourselves? What festivals of atonement, what sacred games shall we have to invent? Is not the greatness of this deed too great for us? Must we ourselves not become gods simply to appear worthy of it?
— Nietzsche, The Gay Science, Section 125, tr. Walter Kaufmann[1]

Though written from a secular viewpoint even Nietzsche seem to recognise what the result of ‘killing God’ is. The result is that without God man must play God.

And in so doing those who think themselves wise have become fools. Who could truly want men as gods? All we have to do is watch how man acts to know that that is pure foolishness.

Man might get rid of God in his mind, but all man has to replace Him is a world of foolishness and despair.