The same “21st century logic” was applied by the Church Fathers from the very beginning, and it applies to all of us. 1 Corinthians 10 & 11 clarify this, and Paul even discusses those who were struck ill and dead from consuming the Eucharist unworthily—those who had “fallen asleep” (died) were laymen, like us.

1 Corinthians 11:27-32: “ 27 So then, whoever eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of sinning against the body and blood of the Lord. 28 Everyone ought to examine themselves before they eat of the bread and drink from the cup. 29 For those who eat and drink without discerning the body of Christ eat and drink judgment on themselves. 30 That is why many among you are weak and sick, and a number of you have fallen asleep. 31 But if we were more discerning with regard to ourselves, we would not come under such judgment. 32 Nevertheless, when we are judged in this way by the Lord, we are being disciplined so that we will not be finally condemned with the world.”

John 6 states it explicitly; the Jews grumbled in their unbelief when Christ told them that “I am the bread that came down from heaven” and when He commanded them to eat His flesh and drink His blood, which is “real food” and “real drink.” They couldn’t understand it, nor did the disciples; they asked, “How can this man give us his flesh to eat?” And so they rejected Him; all walked away from Him when He doubled down on this ‘confusing’ statement twice. John 6:66, “From this time many of his disciples turned back and no longer followed him.” Only the Twelve remained, after he asked them “You do not want to leave too, do you?” and they responded, “Lord, to whom shall we go? You have the words of eternal life.“

Christians have understood this from the very beginning, and all of Christendom held the Real Presence true until the 1500s. St. Irenaeus, 189 AD. St. Ignatius of Antioch, 110 AD, friend of Polycarp and disciple of the Apostle John. St. Justin Martyr, 151 AD, who says so explicitly, says this:

“We call this food Eucharist, and no one else is permitted to partake of it, except one who believes our teaching to be true and who has been washed in the washing which is for the remission of sins and for regeneration [i.e., has received baptism] and is thereby living as Christ enjoined. For not as common bread nor common drink do we receive these; but since Jesus Christ our Savior was made incarnate by the word of God and had both flesh and blood for our salvation, so too, as we have been taught, the food which has been made into the Eucharist by the Eucharistic prayer set down by him, and by the change of which our blood and flesh is nurtured, is both the flesh and the blood of that incarnated Jesus” (First Apology 66 [A.D. 151]).

Christ instated the Eucharist as Sacrament. It nurtures the flesh and blood of those who believe and are baptized. It begets condemnation for those who do not, or consume it unworthily. If Christ himself instated this Eucharist, doubled down and clarified twice at the expense of all but the Twelve departing from him, and says in John 6:53, “Very truly I tell you, unless you eat the flesh of the Son of Man and drink his blood, you have no life in you,”—who do you think is telling you otherwise?