I believe that sacrifice in the old testament serves as a reminder that our denial of our spiritual true selves leads to destruction.
I utterly reject the notion that God is incapable of forgiving us unless someone gets butchered on a cross. That is an ancient interpretation ascribed by minds capable of believing that throwing your child in a fire will give you a lot of sheep. Utterly ridiculous and extremely disrespectful towards God.
The true purpose of the cross for me is to reveal to me that true life is not a result of desperately clinging to my own interpretation of what ought to be, but by embracing life as a gift from a loving God even if it comes wrapped in the shape of a cross.
Jesus died because his message threatened the status quo of those in power, simple as that. He died as all of us will. What made him special is that he did not resist death but accepted it as part of life and trusted God in it even though he did not understand completely what was happening.
By refusing to view himself as separate from God, even in the face of death on a cross, he leads those willing to embrace his example into a life of connectedness with God, ourselves, others and the entire universe. This, I believe, is the salvation offered to us in the man Jesus. As such, his willingness to sacrifice his physical body to a higher ideal that we all can embrace is the true power of the cross.
If we dare to believe that Jesus is a revelation of God/Universe in which we are accepted, then we do not need forgiveness and our sin, which is our steadfast insistance that we are separate from, is removed from us. If we insist that we are alone/removed from God then this very belief will create our reality and make us unable to receive forgiveness.