If God had left us in the dark, not telling us anything at all about Himself—then I would have to agree with you.
But listen: God hasn't left us in the dark! Instead, He has reached out and revealed Himself to us—and the evidence is all around us. How has He done this? One way is in His creation, the universe, for everywhere you look you see His footprints. The Bible puts it this way: "For since the creation of the world God's invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that men are without excuse" (Romans 1:20).
But the greatest way God has revealed Himself to us will stagger your imagination: He became a man! Jesus was not just another religious teacher. The Bible says He was God in human flesh. Do you want to know what God is like? Look at Jesus Christ, because "God was pleased to have all his fullness dwell in him" (Colossians 1:19).
I realize you may not accept this right now—but what if it is true? Then you could not only know what God is like, but you could also have a personal relationship with Him, because Jesus came to bridge the gap between God and us—a gap caused by sin. Look honestly at Christ as He is found in the pages of the New Testament, and your life will never be the same.