Participation is the actual going to Mass, genuflecting, kneeling, standing, sitting at the appropriate times. Many followed the Mass in their Missal. Even the few who said the Rosary were participating by their actual presence.
How pre-conciliar congregations are portrayed by modern, liberals is completely false and nonsensical. People left the Church in droves during the '70s not because of the Novus Ordo but because of the indifferentism that was preached to them from the pulpit. They were told that their Church had been wrong for centuries up until Vatican II so if that was the case why should they believe that the Church had suddenly got it right.