Section I, Part III, Number 36 of the Catechism of the Catholic Church states regarding the knowledge of God:

“Our holy mother, the Church, holds and teaches that God, the first principle and last end of all things, can be known with certainty from the created world by the natural light of human reason.” Without this capacity, man would not be able to welcome God’s revelation. Man has this capacity because he is created “in the image of God”.

The first thing that you should note is the authority by which the statement is made. Not by the Holy Word of God, but by the church. Second that God can be known strictly by the created order in the universe. Third, they state that if this were not so, conversion would not be possible, since man is created in the image of God.

I agree that every human being is created in the image of God, but that due to the fall of Adam, man is dead in his transgressions. As the Apostle Paul says in Ephesians 2:5:

Eph 2:5 “even when we were dead in our trespasses, made us alive together with Christ–by grace you have been saved–”

So we see from God’s Holy Word that even though the light of nature reveals the glory of God, the natural man cannot and will not respond since he’s dead in his sins. The only way for a dead man to respond is to be resurrected by the Spirit of God unto salvation.