The theological doctrine of Jesus dying for the sins of humankind was first worked out over 900 years after Jesus' death by Anselm of Canterbury, an early Christian theologian.
The atonement theology has effectively taken away believers' focus on the teachings of Jesus to what those teachings meant.
In other words, Christianity has become a "belief-based" faith and not an "action-based" faith. People have been taught to worship Jesus rather than follow him.
The idea of being a blood sacrifice to God would have no doubt disgusted Jesus. Both he and John preached a doctrine of repentance, not sacrifice. It was Paul, the gospel writer John and later additions to the synoptic accounts that believed in spilling blood on the altar to redeem us from sin.