I don’t refuse, but since I didn’t get an answer to my question (which is a theological reason for the switch with a little more depth than you like it more), I am gonna wait until mine is answered.
The Mass is a sacrifice and a sacred meal. Is not the Last Supper the pre-eminent model for the Mass?
Perhaps you do not appreciate it, but I think the sense of Sacrosanctum Concilium is valid:
“The faithful should be led to that fully conscious, and active participation in liturgical celebrations.” Something more is required than mere observation. “The faithful should take part fully aware of what they are doing, actively engaged in the rite, and enriched by its effects.”
In the reformed liturgy the priest is able to celebrate facing the congregation (“versus populum”). This allows for
more explicit inclusion in the celebration and participation by the faithful. This was also encouraged by having the celebration in a language they could understand.
“Versus Populum” also enhances positive theological elements which received new emphasis such as the
universal priesthood, the universal call to holiness, the communal dimensions of the Eucharist, and a deeper awareness of baptism as an initiation into the full Eucharistic life of the Church as "a chosen race, a royal priesthood, a holy nation, a people of his own. (1 Peter 2:9)
Versus Populum:
- Did not Jesus face the people He was interacting with? Did Jesus not celebrated the Last Supper facing the apostles? Does not Jesus mediate a better covenant? Hebrew 8:66 "Now he has obtained so much more excellent a ministry as he is mediator of a better covenant, enacted on better promises."
- VP emphasizes the horizontal, Immanent theology of the liturgy as the work of the people of God, as opposed to a sacrifice offered exclusively by the priest and merely aided by the prayers of the people. Since the Council Fathers had seen the Constitution of the Sacred Liturgy in light of empowering the People of God and teaching them that they also share in the common priesthood, a greater participation of the laity was encouraged in the Novus Ordo. We can see the participation of the laity, both man and woman in a much fuller way with more emphasis on their participatory role as royal priesthood. It avoids the sense that the people are an addendum to the priest’s liturgy
- It enables the people to see more clearly the actions going on at the altar in the course of the Mass and so to enter into a deeper understanding/appreciation of those actions. It improves people's ability to hear and understand the spoken words of the Mass better.
- It is the historically authentic practice of the early Church.
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But you have already dismissed the practical advantages of visibility, clarity and explicit signs and gestures of inclusion. So I must simply leave it as a disagreement of theology and priorities. If you want to call it “dumbing down” I cannot stop you.