The priest you spoke to had it backwards. Here is St. Justin Martyr, writing in about 155 A.D., describing to the Roman Emperor Antoninus how the pagans were copying the Christian Eucharist.
"For the apostles, in the memoirs composed by them, which are called Gospels, have thus delivered unto us what was enjoined upon them; that Jesus took bread, and when He had given thanks, said, 'This do in remembrance of Me, this is My body'; and that, after the same manner, having taken the cup and given thanks, He said, 'This is My blood; and gave it to them alone.' Which the wicked devils have imitated in the mysteries of Mithras, commanding the same thing to be done. For, that bread and a cup of water are placed with certain incantations in the mystic rites of one who is being initiated, you either or can learn." - St. Justin Martyr, First Apology, 66
1 Cor 11:22 dispels the concept that the Eucharist was just a meal. They weren't serving steak and potatoes with a side of Eucharist. For the Apostle tells the Corinthians that they have homes in which to have their meals.
Rather, something deeper happened at the Last Supper, something that originated back in Exodus.