The people around Christ when he first adumbrated the Eucharist knew clearly what He was about. "Can this man give us his flesh and blood to drink?" ... and when most of his followers had left him he turned to Peter and the remaining Disciples."And you, My Friends, Will you now leave me?"
There was no misunderstanding. The people who heard Christ knew He was claiming to offer them his Flesh and Blood to eat and drink. Most of them left him. "This is a hard saying and who will bear it?"
The Eucharist - the Sacrifice of the Mass - wasn't some accretion made up by Gentile greeks: Christ claimed it and insisted upon it from the first. "Unless you eat of the Flesh of the Son of Man, and Drink of his Blood, you shall not have Life within you".
The sacrifice of the Cross would be regarded as even more impossible, as it speaks of an infinitely greater event than a man they can see who can turn into a piece of food they can munch. Gentiles had indeed come up with the latter in some of their religions (what C.S. Lewis calls a Corn King). But Isaiah had prophesied the former infallibly by the Holy Spirit.
History's own time line shows that it isn't Jews who first started talking about Jesus that way in their doctrine; it was Gentiles.
And by its very exclusivity, the "have to attend a Catholic held earthly Eucharistic service" interpretation comes at a contradiction with the biblical assertion that the Jewish saints are saved along with the new church. And even the RCC makes its own noises about how some may be visited with these graces despite never attending a Catholic service. These people obviously get life, from Christ.
If, however, you recognize that the body and blood is something that all Christians get, all the time, and that the purpose of the communion ritual is to remind them of this in the same manner that the seder did, then the problem vanishes.