Could it be that these sacrifices were also to put meat on the table? In those days there were not supermarkets to buy meat. They would have killed animals whether there was some ritualistic meaning behind it or not so they could eat. It is meaningless to atone for sins in such a way, especially if the sin is murder, because it doesn't make the victim any less dead. Anyone with common sense can see that.
As far as Jesus' purpose, I think it was similar to Buddha's and many others . . . to teach the rest of the world how to conduct ourselves and treat others. People didn't learn, because emphasis was placed on his death instead of his life. This enabled people to continue with their wicked ways, because their sins are paid for anyways. They will not be held accountable. That's why I lean toward karma, because the Bible says God is just. A just God would make the guilty party pay, not some innocent person.
Jesus died because usually people that try to do what is right are killed by evil people, i.e., Ghandi, Martin Luther King Jr., Abe Lincoln. Many people do not want peace, and they eliminate those that try to bring it to keep the world in the state it is in.