Jesus himself teaches us that the Church is to observe the Supper ‘in remembrance of me’. The word remembrance is the Greek word which literally means a memorial. The Supper is no altar of sacrifice, but a table of remembrance, a place of spiritual communion with the Saviour by his Spirit. To teach that Christ has instituted a means whereby his sacrifice can be perpetuated through time is to contradict the plain teaching of Scripture.
This becomes yet clearer from the identification of the Lord’s Supper with the Passover memorial of the Old Testament. The Lord’s Supper was first celebrated at the time of the Jewish Passover and Jesus specifically identifies it as an equivalent when he says: ‘I have earnestly desired to eat this Passover with you before I suffer’ (Luke 22:15). What exactly was the Passover? It was an annual feast established by God in which the Jews would remember the night in which the angel of death ‘passed over’ those families which had applied the blood of the lamb to their door-posts (Exod. 12:1-13). ‘Now this day will be a memorial to you, and you shall celebrate it as a feast to the Lord; throughout your generations you are to celebrate it as a permanent ordinance’ (Exod. 12:14). This was a ‘memorial’ to a specific act of God in redeeming his people from bondage and death. The ‘memorial’ served to bring to remembrance an important event. It did not repeat the event but kept it vivid in the memory through a physical representation.
Just as God instituted a memorial of remembrance of redemption in the Old Testament, he has done the same in the New Testament. 1 Corinthians 5:7 states, ‘For Christ our Passover also has been sacrificed.’ His death is an accomplished fact. Now we are called, not to a sacrifice, but to a feast: ‘Let us therefore celebrate the feast . . . with the unleavened bread of sincerity and truth’ (1 Cor. 5:8). When Christ states that the bread is to be eaten and the wine drunk in remembrance of him, he is employing the same language as that of the Old Testament memorial in reference to the Passover. The Lord’s Supper is not a sacrifice, it is the commemoration of a sacrifice.
Jesus didn't die on an altar anyway.
There was no altar at the Last Supper, they were reclining at the dinner table.
Altars are only for offering actual sacrifices. We don't offer the sacrifice of Jesus to god for our sins. He's not some thing we manipulate like that.
Jesus gave Himself up for our sins. He laid down His life on His own to take the punishment for our sins, dying in our place.
To treat Jesus as if He's some kind of animal to be brought to God by us to be slaughtered for our sins denigrates Him terribly. What an affront to God.