Scripture interprets Scripture. It must be consistent.
Since the disciples were still under the Law at the time of the Last Supper, they would not have drank the cup even suspecting that it was blood as that would have violated the Law and made them unclean. And Peter states in Acts that he had never eaten anything unclean.
Not to mention that the Council of Jerusalem which again reiterated the prohibition of eating blood, with no exceptions, the Catholics claim was presided over by Peter.
Communion being a symbolic representation of a spiritual truth just as the Passover meal they were eating when Jesus instituted communion represented the original Passover in Egypt that they did to REMEMBER is consistent with the rest of Scripture.
If Catholics think that eating the wafer is somehow going to save them, they are basing their salvation on their works and their effort instead of the finished work of Christ on the cross.
Jesus died once for all. It's over and done with. He is not the perpetual sacrifice, He is the great high priest, living to make intercession for us, the only priest we need.
Catholics can't even get who Christ is and what He's doing right. Sheesh....
By that criteria, the Real Presence is true. It's in the Gospels and epistles, Christ's words make it very clear, all consistent with each other and Paul warns specifically against the view you hold.
Now what?