Belief in the Creator is such a critical choice in a person's life because there is no excuse that God will accept for denying Him.

Psalm 19 1-4  "The heavens declare the glory of God; and the firmament shows his handiwork.  Day unto utters speech, and night unto night shows knowledge.  There is no speech or language, where their voice is not heard.  Their line is gone out through all the earth, and their words to the end of the world. In them he has set a tabernacle for the sun..."

God is evident in all that we see in his creation.  In every language.  Failure to read the obvious is inexcusable.

Paul explains it this way:  Romans 1: 20-21a  "For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse;  Because that, when they knew God, they glorified him not as God, neither were they thankful; but became vain in their imaginations..."

Every clan, culture, tribe etc. that anthropologists discover has some type of worship.  No matter how far flung around the world, these people groups make a God to worship.  A totem, a golden calf, the sun, a graven idol of some sort.  That one instinct I told you that I believe exists--and our only instinct--is to seek God.

God has said in Deuteronomy 4:29 "But if...you shall seek the Lord your God, you shall find him, if you seek him with all your heart and with all your soul."  If you seek Me, you will find Me is what God says.  In those words, God gives a promise to anyone who is looking for Him.  Substituting anything else will not do.