Isn't that the point? After cataclysmic changes in society from WW1, after the French and the Russian revolutions, the Church did not change.
Having lived through WW2, the bishops decided on a different path. They sought to revitalize the message of Christ so that peace, not war, would be associated with the name of Christians. The rites for the liturgy and sacraments were changed to emphasize their connection to Christ as revealed in Scripture and through our traditions.
Retreating back into our castles and condemning other people had proved disastrous for Pius IX and his successors. Europe was in flames and then in ruins. The exodus from the Church started then, with liberalism, communism, and other movements pulling people away from their home in the Church. The Church was still identified with the old order, with the disorder of war, so many left. It was not liturgical changes, there were underlying social forces that pushed people away.