First, there is a category of gift that includes different individual gifts that may be distributed differently among one group of people that are not at all given to another group. These are called charisms, or charismatic gifts, or graces
gratis datae. A completely different category of gift - called the Seven Gifts of the Holy Spirit, express themselves in stages of maturation, analogously to our physical childhood, adolescence and adulthood. My post referred to , in St. Paul's language, "babes" - or young children - in Christ. A five-year-old boy, for example is still a male human being, possessing the potential - the potency - to be a father. But that potency is exactly that - a potency, a potentiality, but not the actual possibility..yet. In adolescence he does begin to become able to beget a child, physically but not yet emotionally or psychologically. Only in the maturity of adulthood does this gift come to fruitfulness, or fruition. St. Paul was saying that these in Corinth were spiritually young children, or "babies" in Christ. As with the natural "facts of life" as we used to say of human sexuality, childhood is not the time to begin to teach "where babies come from." They are not ready to grasp or understand the facts.
So it is in the supernatural spiritual realm. This realm is not of charisms; the Seven Gifts are different, they manifest in grades - or stages - or ages, beginning with (mere) potency in spiritual childhood, to the beginnings of act in spiritual "adolescence", to glorious sanctity in spiritual maturity or "adulthood". They are placed in importance in the Catechism as given for the perfection of the Virtues (theological and moral). (CCC 1831 - the "In Brief" that follows may also be helpful) Thus, St. Paul wrote to some of the Catholics in Corinth, that still, they were only "babies" in Christ.
And as the Apostle John also acknowledged the stages, or ages, of spiritual maturity (or lack of it):
This acknowledgment manifests the actual spiritual fatherhood of the Apostle, and opens doors of depth in understanding others in the Church. It needs to be said: Spiritual maturity has nothing to do with chronological natural maturity, or even number of years "a Catholic." Nor is it necessarily linked to formation in a religious order, or education and advancements in the clerical hierarchy.
The best introduction to this spirituality that I know of is
The Ordinary Path to Holiness (disclosure: I know the author). A deeper and broader presentation (and free) in the EWTN Library is
The Three Ways of the Spiritual Life. The spirituality itself is best described by St. John of the Cross.