For all of historical Christendom - the Body and Blood of Our Lord has been a central mystery. The few who deny that Truth are flat out heretics, they have simply lost all sense of Grace and Truth. Pity them and pray for them, as they have no way to know their error absent God’s free Grace.
You're slipping!
For most of Historical Judaism, the Passover meal WAS known for what it was: a REMEMBERANCE of GOD's saving power.
When Jesus announced that the bread and wine represented HIM - then no WONDER that folks, at that time, said it was a 'hard teaching'.
It's only a mystery to those who accept what they are told, that it's a mystery...
Those who read and believe the bible, not so much...