Human sacrifice was common throughout the ancient world from Greece to India and beyond. Judaism strongly opposed it. Even so traces can be found both in regard to Abraham’s test and examples in the Books of Kings of human sacrifice by Israel’s neighbors.
Similarly, resurrection after death, a staple of contemporary cultures, only appears explicitly much later in Judaism in response to persecution and exile. I suggest that the opinions of the rabbis about how to respond to the sacrificial system after the Temple was destroyed were a reaction to competing religious ideologies.
There is a thread in Christianity that claimed that it was superior to Judaism. Abraham had failed God’s test of him. He had not killed Isaac. Whereas the God of Christianity had killed his son Jesus. Jesus was the Sacrificial Lamb. He was killed over Passover as a replacement of the Paschal Lamb that Jews offered in Temple times.
It was this sacrifice that heralded the end of the Israelite system of sacrifices. They were no longer needed. Christianity had taken over. They had served their purpose and been replaced by a new order.
The Jewish position initially was the sacrifices had merely been suspended by the loss of the Temple. And as with the destruction of the First Temple, they would soon be reinstated. The idea that God would want a child, any child to be killed to serve His purpose was repulsive to them. If anything, it was proof to them that Christianity had a false Messiah.
And this is why the rabbis insisted that nothing should be done outside the site to imitate what was once done in it. That was why it came to be forbidden to have a roast lamb at the Seder table. So as not to think that this was a replacement of the formal Temple based ritual.
This why unlike Christianity they were simply not prepared to accept the idea that the sacrificial system was over. They looked forward to its return as a response to Christianity. Hence this idea entered the liturgy as a crucial component. Its importance is not just historical but also theological.