Show me where Jesus endorsed slavery.
He, and his apostles, did have instructions for those who found themselves in that status - which is very similar to their instructions to those of us who find themselves subject to a modern government. Those instructions were to accept your situation (including the status of women in those days) and focus on eternal issues. Jesus did not come the first time to change all the institutions of humanity (that is coming soon). He had a specific mission to accomplish and he did not want His disciples getting involved in politics and revolution. He had bigger fish to fry.
Vicarious redemption is far older than "archaic". It is older than "primordial". It has been God's plan before time began.
It is the one thing that puts man into the right relationship of dependence on God. Without that we tend to elevate ourselves to a place where we eventually rebel against God. He's had quite enough of that with Satan and his angels.
So this world is a test range to see who will make that simple attitude adjustment. The test is so simple it doesn't need any updating to 2016.