The idea of an earth that is millions/billions of years old came from the belief that the fossil record was built up over a long time. But this creates an insurmountable problem regarding the Bible’s gospel message. The fossil record consists of the death of billions of creatures. It is a record of death, disease, suffering, cruelty, and brutality—a very ugly record.
The Bible is adamant, though, that death, disease, and suffering came into the world as a result of the sin of Adam. God instituted death and bloodshed because of sin so mankind could be redeemed. As soon as Christians allow for death, suffering, and disease before sin, then the whole foundations of the message of the Cross and Christ’s Atonement have been destroyed. Original sin is wiped out.
If there were death, disease, and suffering before Adam rebelled, then what did sin do to the world? What does the apostle Paul mean in Romans 8 when he says the whole of creation groans in pain because of the Curse of Genesis 3? How can all things be restored in the future to no more death and suffering, unless the beginning was also free of death and suffering? The whole message of the gospel falls apart if one allows millions/billions of years for the creation of the world.