Repentance and obedience is all that is necessary now but that doesn't mean a blood sacrifice was unnecessary in order to achieve that reality.
The point is a person could offer a sacrifice without being sincere or be sincere without the accompanying sacrifice.
Jesus taught of a spiritual rebirth predicated on sincere faith, receiving forgiveness from a God who has always been the same. God did not suddenly become forgiving because an innocent man was put to death. Jesus excoriated those who would reject him and seek his destruction. On the cross he asked the Father to forgive those who were killing him.