Existentially, the Eucharist is indeed the source and summit, the center and foundation of all that the Church is and is supposed to be. But historically, the Eucharist —if we mean by that what the Church now celebrates— came from the Church, not vice versa. It took the Church, under the guidance of the Holy Spirit, more than three centuries to learn how to celebrate and begin to understand the eucharistic mystery as we now celebrate and understand it.
They approached the matter backward. Instead of looking first to the Christ-event and letting that define their thinking, both Protestants and Catholics first defined sacrifice phenomenologically and then applied that definition to the Mass. An awareness of the content and structure of the classical Eucharistic Prayer, which could have been a corrective, was no longer present in the Western Church.
… applying to the Mass ideas of sacrifice taken from the Old Testament almost as if Christ never existed.
Robert J. Daly, Robert Bellarmine and Post-Tridentine Eucharistic Theology, in Raymond F. Bulman & Frederick J. Parella, editors, From Trent To Vatican II. Pàgines 88, 96 i 97.