The Rosary was often referred to as the “Lay Man’s Psalter” in the distant past. The clergy have been and are still required to pray the Divine Office also known as the Liturgy of the Hours. The DO has prayers that correspond to the various hours of the day, e.g. Matins, Lauds (in the morning), Prima (first hour of the day), Tertia (third hour of the day), Sexta (sixth hour of the day), Nona (ninth hour of the day), Vespers (late afternoon), and Compline (evening prayer). In praying the DO, the clergy would effectively pray all 150 psalms. Since lay people cannot take off from work and their daily lives as easily as those in monasteries, the Rosary gave them a way to pray that sort of mimicked the Divine Office. Each Ave Maria was supposed to take the place of a psalm. My understanding is that the Rosary has undergone some evolution over the centuries, and that in many places it only consisted of the Aves and the mysteries in between. The Pater Nosters and Glorias may have been added later. Certainly the O Jesus Fatima prayer could only have been added in recent times, and at many churches I have heard people add additional prayers to the end of the Rosary. Our family adds the Salve Regina, and we ask the patron saint of each of our family members (mom, dad, and five kids) to pray for us. We also invoke the saint or saints of the day, which often results in discussion after the Rosary about saints with particularly interesting names, e.g. St. Leander for today.
We do not use the Luminous mysteries. They are an option, just like using the Memorare versus the Salve Regina after the Rosary. We opt not to use them. I don’t think there is anything wrong with that. Btw, I’m a Knight as well, so the Rosary is a particularly special devotion for me.