Then do we just throw out all the tenses throughout all of scripture that describe God? That doesn't make sense, does it? You assume it is an error because you don't agree with what it says. That is ok - that is up to you, I don't expect to change what you think. But you do have to remember that He gave us His Word - both written and in the flesh so that we can know Him. To not make it apply would mean that He is the author of confusion - and we know that He isn't.
It's either Heb 9 or 10 which speaks of Christ as entering the heavenly holy of holies "not with the blood of bulls and goats, but with his own blood," and says that he *will* appear a second time (that is, at the Second Coming). This is a direct reference to the Temple liturgy for Yom Kippur, in which the High Priest entered the holy of holies (the only time he was permitted to do that).
This means that Christ is an eternal priest ("you are a priest forever, in the order of Melchizedek"). Priests offer sacrifices, eternal priests offer eternal sacrifices.
Plenty of references in the Church Fathers to the Eucharist as a "sacrifice," going back all the way to Apostolic times. Christ's suffering ended at Calvary, but his priesthood did not.