Back in the middle of the 19th century (1800s) a liturgical movement was born in some of the German and French Benedictine monasteries. As the liturgy is the center of a Monks life; they wanted to understand it better and celebrate it more beautifully. As those involved began researching historical records, as is usually the case, the further back in history that they went the less records they could find. So to bridge the gap between what we knew about the Last Supper and the rites of the Temple of Jerusalem before its destruction in 70AD and the oldest records that we had from the 4th and 5th centuries: they began a new science— Liturgical Archaeology.
In their studies they made an erroneous assumption. When they learned that the altars of the four major basilicas of Rome (the oldest Church buildings of Christendom) were originally built as they currently stand, away from the wall of the apse where a priest could walk around it, and that as you stood behind it and looked toward the nave you were facing east—they assumed the people faced west and the priest and people faced each other and the Masses from the early 4th Century until the 7th were celebrated “ad populum” (towards the people).
Msgr, Klaus Gamber (one of Pope Benedict’s seminary professors) discovered the mistake and pointed it out in a book he wrote that it was true the priest faced east toward the nave and the main doors of the basilica, but so did the people—they all faced the same direction and the priest offered the Sacrifice of the Mass behind the people. As at the moment of consecration the huge 5 story doors on the east end of the basilicas would be opened and the rising sun would shine exactly on the altars. This was not practical in Northern Europe so as Catholicism spread there the churches were turned around the other way with the back wall facing east and thus the priest began offering the sacrifice of the Mass in front of the people as they all continued facing the same direction—EAST. The rising sun was not visible, so they began building a reredos over the altar attached to the back wall with all of its beautiful statues and intricate carving and artwork gave a vision of heaven and eternity, and this became our tradition for nearly 1500 years (nearly 7 times the age of the USA).
So, “ad populum” was never a tradition in our faith and was never done until 1969. The Lord told us that by the fruits you will know the tree (Matthew 7:18). The liturgy is the center of our lives in the Church, to claim that our liturgy is great while the Church literally falls into deep decline is a contradiction. “Lex orandi, Lex credendi” from the laws of worship come the laws of belief.