He put the new covenant in His own blood into the hands of His friends, and we turned it into a sacrament. Read Hebraically, the cup is a covenant cut once and sealed forever, not a rite to be re-administered on a schedule by a professional. A sealed covenant cannot be re-sealed, and the covenant that retires the mediator was quietly rebuilt into a priesthood. Why I refrain, and what is still left at the table.
Pentecost is not the Church's birthday. It is the appointment HaShem set on His calendar before Israel had a calendar. Shavuot was already there. The Ruach was already moving. You are grafted in, not displaced.
A structured introduction to Hebrew and Greek intellectual frameworks — and why the lens you bring to Scripture determines what you actually hear it say.