I read a non-Catholic minister write how attendance at Sunday services and other worship services had diminished over the past years. He pointed to how, unlike Catholics, there was no Vatican II to blame.
It is a reality of the 20th Century, and now 21th Century that our lives are busier. There are more distractions. It was why Vatican II was convened, to bring the Gospel message to the modern world.
The Gospel message is essentially one of love and mercy. St. Paul brought that message initially to a pagan world. Over time, rich devotions have developed withing the Catholic Church as response to that mercy and love. The First Friday devotion is simply one of those devotions.
What I tell people about my Catholic Faith is that it is simple enough to be summarized in the Apostles Creed, yet rich enough that I can never reach its depths. The Catholic Church has a boundless richness of devotions that have developed through the ages from the Stations of the Cross to the Rosary, to different Novenas. There are many different ways for an individual to express personal Faith. Different parishes provide different services according to resources.
Vatican II did not change any Church teaching. It’s documents are readily available to the public and I highly recommend them. What sets the Catholic Church apart from other denominations is that we do not rely on scripture alone, but accept Tradition, and the magisterium to protect both scripture and Tradition by the power of the Holy Spirit. Vatican II was a gathering of the magisterium and its documents were the result.