"Then the LORD saw that the wickedness of humanity was great in the earth, and that every intent of the thoughts of heart was only evil continually." (Genesis 6:5)
God had told Adam and Eve what the judgment for disobedience would be…
“…you must not eat from the tree of the knowledge of good and evil, for when you eat from it you will certainly die." (Genesis 2:17)
God's destruction of humanity by the flood did not rid the world of sin, just reduced the number of evil people…
"So the LORD said, I will destroy humanity whom I have created from the face of the earth" (Genesis 6:7)
With that flood God introduced how He intends to finally deal with humanity - His GRACE…
"But Noah found GRACE in the eyes of the LORD" (Genesis 6:8)
Humanity continues to be sinners falling short of the glory of God, and the judgment of God is still death, but in His Grace He intends to save humanity out of death.
“…all have sinned and fall short of the glory of God…the wages of sin is death, but the free gift of God is eternal life…for the GRACE of God has appeared, bringing salvation to all humanity.” (Romans 3:23; 6:23; Titus 2:11)
The ARK delivered Noah and his family from the flood but they eventually died. Jesus will deliver all of those involved in the flood, and the rest of humanity from death into a n ew immortal life without sin. That is the promise of God, whether people believe it now or not.
“The thief comes only to steal and kill and destroy; I came that they may have life, and have it abundantly…it is a trustworthy statement, deserving full acceptance, that Christ Jesus came into the world to save sinners…God our Savior…wills that all humanity be saved and to come to the knowledge of the truth. For there is one God, and one mediator also between God and humanity, the human Christ Jesus, who gave Himself as a ransom for all…It is a trustworthy statement deserving full acceptance. For it is for this we labor and strive, because we have fixed our hope on the living God, who is the Savior of all humanity, especially of believers.” (John 10:10; 1 Timothy 1:15, 2:3-6; 4:9-10)