The Genesis Flood is a pivotal event in human history. In the Flood, God destroyed all of humanity, save eight souls, as well as all vegetation and the vast majority of animals. Because of the Flood’s massive and sudden destruction, living things were quickly buried under enormous amounts of water and sediment, forming most of the fossils we have found in modern times.
A denial of Creation goes hand-in-hand with a denial of a world-wide, catastrophic Flood. If God created the world in 6 literal days out of nothing by His spoken word (and He did), then He is in charge and we must submit to Him. If the Flood is true (and it is), then God intervenes in the affairs of man and judges for sin; we are accountable to Him.
Denying Creation and the Flood attacks the basic tenants of salvation: (1) that God is sovereign and we are obligated to worship Him; and (2) if we rebel against God beyond the point of His mercy, we will be judged eternally for our sins, not to mention (3) our duty glorify God.
Genesis 1 teaches us very important truths, not only about our existence, but also about the worthiness of the Creator God to receive worship and about our responsibility to submit to Him for everlasting salvation.