Not any person receives this prophetical « munus » (function, responsibility, task …) in the Church: ‘Teaching Spiritual Life’.
It is not an obvious, systematic, automatic, easy task/vocation in the Church. ‘Teaching spiritual life’ is not the property of Priesthood, even if all priests have a share in that responsibility of teaching some “spiritual life” to their flock. It is a specific Call/Vocation that one receives, clearly or in a more progressive way. It belongs not to the ‘Sacerdotal function’ of the Church, but to the ‘Prophetical function’.
Note: To know more about the three functions of the Church, (Royal, Sacerdotal, Prophetical) please see John Henry Newman, ‘Preface to the Second or Third Edition’ to his “Via Media” from §2 n°4 when he says: “With this introduction I remark as follows…”.
The ‘Prophetical function’ of the Church provides some important elements in the Church’s vitality: the Universities (Institutes, Schools, …), all types of Consecrated life (except Parish Priest vocation). Name it: Monks, Religious, Virgins, Hermits, Secular orders, and some forms of consecration in the recent movements in the Church. You may add the private consecration as well. And we have to add: Spiritual Institutes, Retreat places,..
Amongst all the people who belong to this great lateral (or diagonal, diachronic) wing of the Church, this 'Prophetical function' of the Church, you’ll find that Call to serve in a very specific way the 'teaching of spiritual life'. Not all who belong to the 'Prophetical Function' of the Church are called to teach Spiritual Life. Only some of them.
Normally, the “Parish Priest” is supposed to be able to teach at least the 4 sections of the Initiation into Christian life:
1- the Creed,
2- the Sacraments,
3- the Commandments, and
4- the Our Father.
You’ll happily find that these 4 traditional parts of the mainstream teaching of Christianity composes the 4 Parts of the Catechism of the Catholic Church.
If you study theology, the mainstream theology, the 4 first years, to become “Licentiate in Theology”, you’ll find that a lot of what you receive is simply summarised in the 4 parts of the Catechism.
I am sure, you’ll easily admit that the Fourth Part of the Catechism of the Catholic Church, the one that teaches Prayer, the Our Father, and a bit of “spiritual life” only gives a small glimpse of the immense richness of the Church in this field.
Note: Lateral thinking: Shaping “Integral Theology”
The actual teaching of theology in the Catholic Universities, engineered (shaped) and lead by theologians who often belong to the Sacerdotal Function of the Church (or at least who shifted towards it), gives the teaching a more 'Sacerdotal' nuance than a 'Prophetical' one. In the sense that, if you belong to the 'Prophetical Function' of the Church, you’ll find that the Curriculum is particularly poor in “Spiritual life”, and that all its sections (Dogma, Bible, Sacraments, Moral Theology,...) should be taught in a more “spiritual way”, without though loosing any scientific or academic quality.
You can’t imagine a different teaching of theology, a different ordinary ‘magisterium’ (teaching) else than what you’ve got. This is why it is very difficult for you to imagine what would be the teaching of theology (Integral Theology), or/and the teaching of “Spiritual life”, made by a Master in “Spiritual life”, a proper teacher of “Spiritual Theology”. He forcibly belongs to the Prophetical function of the Church.
I am sure that we can have a “Theology” made by the 'Prophetical function' of the Church, and it would be really wonderfully made. Integral Theology. Just imagine…