But public revelation is the only one that people must listen to and grant their assent to.
Agreed. What one “must” do is the minimum, though. Daily Mass, which you attend, goes beyond the minimum. To really grow in the spiritual life and become more one with God, we are unwise to limit ourselves to the minimum of what He offers us. To do only what we “must” do, not doing any daily prayers beyond the Mass on Sundays and not going to Confession any more often than the minimum attendance required of us, is not conducive to spiritual growth. Practicing Daily Mass like you, or praying daily, helps one’s soul a lot. So do the devotions offered by the true apparitions of Jesus and Mary. Seeking to do only what we “must” do leaves the soul less fruitful and more susceptible to threats from the enemy than is a soul that’s trying to do all it “can” do to be one with God.
Private revelation does not require that and it can not surpass nor add to public revelation.
It cannot “surpass” public revelation in ever being more important than public revelation, nor can it “add” to public revelation in becoming a necessary part of one’s faith as a Catholic. It
can, however, expound upon public revelation. They can also teach things not included in public revelation but neither contradictory to it nor necessary to people’s faith as Catholics. Often, apparitions or Church Fathers feel free to elaborate on the public revelations of God’s relationship with humanity, expounding on them, discussing specifics of philosophy or theology that aren’t explicit in the public revelation.
The true apparitions never contradict the Church’s infallible teaching or tradition. They can illuminate our understanding, though, and teach us things not already made explicit. It’s no coincidence that many of the people proclaimed “Doctors of the Church” saw apparitions and heard from God’s Spirit in uniquely powerful ways.
Therefore listening to the apparitions and practicing their devotions is very valuable in building the spiritual life. This is especially true since the devotions of apparitions of Jesus and Mary often offer special outpourings of grace, and the Church is perfectly accepting of the possibility that God pour out grace through special means like relics, statues or devotions. This is the same as with Daily Mass. Just as Daily Mass or Eucharistic Adoration offer a special outpouring of grace for those that participate in them, so the devotions of the apparitions offer additional grace.
So anything said in the private revelations must already be a part of the public revelation, so do we really need it? Can we not just follow the public revelation?
Not everything said in the private revelations is in the public revelations. For instance, prophecies of future events. These always come true when it’s a true apparition, such as Our Lady of Fatima or Our Lady of Good Success. Also, the special opportunities to receive grace that come through the devotions of apparitions are passed over by those that stick only with what they must do rather than going beyond it to what they can do as well. The apparitions’ devotions, such as the Rosary and others, offer special growth of spiritual life that people don’t experience when they stick with the minimum of what the Church teaches. This is NOT what you are doing, for you go to Daily Mass and I imagine you pray more often than just at Mass and Confession. You are doing more than the minimum, or what you “must” do.
Devotions from apparitions, like Daily Mass or daily prayer, offer additional parts of grace that help people to grow in fellowship with Christ Jesus. While not “necessary,” they help people’s souls enormously. The goal is to be as close to God as we can be. Doing the minimum the Church requires of us to come nearer to God is not conducive for achieving that goal. Doing devotions Jesus, Mary or the Church offer to help people come closer to God is much better.
I do not need anything extra in my spiritual life, public revelation is enough. It is everything.
What was offered in the beginning of Church history was all knowledge and gifts necessary to the soul’s salvation. It doesn’t offer everything there is that may help a soul on the path to its salvation. Christ, His Mother and His Church have offered more since then, to help Christians. The Daily Mass, for instance, didn’t exist prior to a few generations ago. It is an extraordinary new blessing of grace offered by the Church for its members. Praying frequently also provides special grace and deeper intimacy with God. So does offering to God sacrifices or penances. So does practicing devotions, including and especially devotions offered by Jesus and Mary in the course of Church history for the benefit of the faithful.