Don't you think the whole of the NT is the doctrine of Christ? Including what Paul taught about Communion?
It's not the only thing he said, but it's the last thing he said.
Paul is giving the reason for the Lord's Supper which he had received from the Lord.....you proclaim the Lord's death until He comes.
This is consistent with the other passages regarding the Lord's Supper...."do this in memory of Me."
In none of the passages we have on the Lord's Supper does He say one must physical eat and drink His flesh and blood for salvation.
Hence, why I said context was key to understanding this issue.
23For I received from the Lord that which I also delivered to you, that the Lord Jesus in the night in which He was betrayed took bread; 24and when He had given thanks, He broke it and said, “This is My body, which is for you; do this in remembrance of Me.” 25In the same way He took the cup also after supper, saying, “This cup is the new covenant in My blood; do this, as often as you drink it, in remembrance of Me.”
26For as often as you eat this bread and drink the cup, you proclaim the Lord’s death until He comes. 1 Cor 11:23-26 NASB