But the Bible simply does not bar one from taking communion because of sin or their understanding of "Real Presence."
Read the words of St. Paul.
Paul wrote to the Corinthians: “The cup of blessing which we bless, is it not a participation in the blood of Christ? The bread which we break, is it not a participation in the body of Christ?” (1 Cor. 10:16). So when we receive Communion, we actually participate in the body and blood of Christ, not just eat symbols of them. Paul also said, “Therefore whoever eats the bread and drinks the cup of the Lord unworthily will have to answer for the body and blood of the Lord. . . . For any one who eats and drinks without discerning the body, eats and drinks judgment on himself” (1 Cor. 11:27, 29). “To answer for the body and blood” of someone meant to be guilty of a crime as serious as homicide. How could eating mere bread and wine “unworthily” be so serious? Paul’s comment makes sense only if the bread and wine became the real body and blood of Christ.
There is no valid communion without a valid priesthood. And as for the Catholic Church understanding is intrinsic. Even as children we are taught the Real Presence because we have to know the miracle taking place and believe before we can accept. That is not mere symbolism. We’re not talking Saltines and Welch’s grape juice here.