According to Catholicism, to what extent is the spiritual growth of a Christian impaired by his/her lack of devotion to Mary and the Saints?

According to Catholicism, if a Christian lacks devotion to Mary and the Saints, is he or she spiritually "handicapped" or "missing out" spiritually? For example, let's suppose that a Christian has devotion to the Father, the Son and and the Holy Spirit (or possibly subsets of them in the case of non-Trinitarians). Let's say also that this Christian only prays to God in the name of Jesus, his mindset is constantly set on becoming a better disciple of Christ and he constantly seeks the guidance of the Holy Spirit. However, he has no devotion to Mary or the Saints, to the point that he doesn't even think of them at all, they are just not part of his daily thoughts. His only devotion is God, and God alone. **According to Catholicism, would such a Christian be able to live a spiritually fulfilled life and achieve full spiritual maturity?** Or on the contrary, due to his lack of devotion to Mary and the Saints, would such a Christian inevitably encounter a road block to his spiritual growth, which will become evident to him as a feeling of *"I feel like I'm missing something but I'm not sure what it is"*? ***Note:** For those interested in the Protestant perspective on this issue, please see https://christianity.stackexchange.com/q/87520/50422*