To me that is very clear.
If people want to take Luke 22:20 literally
They would have to say it was the cup that died for our sins.
If people want to take John 6:52-54 litereally,
Then they would have to conclude that Christ was literally referring to cannibalism and their response would be offensive (I hope).
There is nothing mystical about communion. Christ was simply making a point that we must repent to God and accept His death that He paid for the forgiveness of our sins. That is the new covenant. There will not be another covenant. Christ left this sacrament (communion) so that we could proclaim what He has done for us. Communion physically ties us to a direct act of Christ and a way in which we can proclaim Christ. That is a great honor and blessing in itself.