I always laugh a little when people claim that we switched to “ad populm” as if that is a big change. The truth of the matter is that that is the older tradition. Jesus faced the apostles for the most part at the last supper. The early church gathered around the table for “the breaking of the bread”
During persecutions, some times, Mass began to be celebrated in the Catecombs on a tomb. In those instances, the priest had his back to the people.
St. Peter (Vatican city), “St. Paul outside the walls” Churches that are quite old, both have always had the main altar “facing the people”. Many other older churches also a set up that way.
People facing East–I have only heard of that in very recent times.
**The priest facing the altar with his back to the people is actually of more recent development **
Joseph Cardinal Ratzinger - The Spirit of the Liturgy
The Altar and the Direction of Liturgical Prayer
adoremus.org/0500-Ratzinger.html
Turn to the East is essential
"On the other hand, a common turning to the East during the Eucharistic Prayer remains essential. This is not a case of accidentals, but of essentials.
Looking at the priest has no importance. What matters is looking together at the Lord. It is not now a question of dialogue, but of common worship, of setting off towards the One who is to come. What corresponds with the reality of what is happening is not the closed circle, but the common movement forward expressed in a common direction for prayer…
…However, in Saint Peter’s, during the pontificate of Saint Gregory the Great (590-604), the altar was moved nearer to the bishop’s chair, probably for the simple reason that he was supposed to stand as much as possible above the tomb of Saint Peter. This was an outward and visible expression of the truth that we celebrate the Sacrifice of the Lord in the Communion of Saints, a communion spanning all the times and ages… The custom of erecting an altar above the tombs of the martyrs probably goes back a long way and is an outcome of the same motivation… Because of topographical circumstances, it turned out that Saint Peter’s faced west. Thus, if the celebrating priest wanted – as the Christian tradition of prayer demands – to face east, he had to stand behind the people and look – this is the logical conclusion – toward the people… The liturgical renewal in our own century took up this alleged model and developed from it a new idea for the form of the Liturgy. The Eucharist, so it was said, had to be celebrated versus populum (towards the people). The altar – as can be seen in the normative model of Saint Peter’s – had to be positioned in such a way that priest and people looked at each other and formed together the circle of the celebrating community… This is, of course, a misunderstanding of the significance of the Roman basilica and of the positioning of its altar, and the representation of the Last Supper is also, to say the least, inaccurate."