I have been reading that some people have a hard time understanding why Jesus’ death was necessary at all if penal substitution is not the correct doctrine for justification. I would ask for people to read the scriptures again and think about the definitions to the words “redemption” and “ransom.” The apostle Paul argues that we are slaves to sin and children of wrath. “Redeem” is the concept of buying back. Redeeming a coupon means the company that produced the coupon pays you back. There are many places where the scriptures picture this redemption concept.
“Be on guard for yourselves and for all the flock, among which the Holy Spirit has made you overseers, to shepherd the church of God which He purchased with His own blood. (Acts 20:28; NASU)
Ransom carries a similar concept. I think for us it is easiest to think about a kidnapping situation. A kidnapper asks for a ransom price to return the abducted one back to his or her family. The price does not equate the value of the person. Obviously a person is worth more that a few million dollars. But it is the price that is set to satisfy the demands of the kidnapper.
“For even the Son of Man did not come to be served, but to serve, and to give His life a ransom for many.” (Mark 10:45; NASU)
The scriptures teach that Jesus was the ransom and the price was his blood (death). The cross is not substituting us for Jesus. Rather, the death of Jesus was the satisfactory price that could free us from sins so that God could still be just yet also justify us. (Romans 3:26). The Law of Moses taught us that blood is the required price for sins. But the blood of animals is not sufficient a price to redeem us (Hebrews 10:1-3). A higher price had to be paid to free us from sin. The blood of Jesus was the acceptable sacrifice for our sins. If substitution is correct, then I do not understand why God did not say that Jesus died in our place. Instead, God taught us that Jesus was a ransom, redeeming us from sin and death.
I offer this as a simplistic answer while we rest our minds during this extended weekend.