Good question, dont know what i was thinking there Look, the human sacrifice was Jesus laying down his life and as an atonement for mankind. When someone does wrong, they need to be held accountable for it in Gods eyes. The death of Jesus covered that accountability. So what is the beef that you have with this??
Note the part of your post I highlighted. That's the entire problem right there. Under this system, we are not being held accountable for our actions. We are not paying any debt. We are not being punished. Jesus (according to Christian theology) was the person who was punished for my wrong doing. How is that ME being held accountable for my actions?
If my parents grounded my sister because I talked back to them, how does that teach me anything? How am I being held accountable for my action? And importantly, How is justice occuring?
The other half of the problem has already been pointed out. Jesus is God. So Jesus (God) sacrificed himself to pay for a debt we owed him. If he was going to pay it anyway- and not going to make us pay for it (hold us accountable)- why not just say "Okay, it's payed, I forgive you."? What is the purpose of sacrificing yourself in order to forgive someone a debt that they owed to you, and particularly when you can make up any of the rules you want?