A restatement of the exact relationship between liturgy and other public forms of piety:
73. The Church’s teaching on the relationship of Liturgy and pious exercises may be summarized as follows: the Sacred Liturgy, in virtue of its very nature, is by far superior to pious exercises(Cf. SC 7), and hence pastoral praxis must always accord to the Sacred Liturgy “that preeminent position proper to it in relation to pious exercises”( CDWDS, Circular letter Orientamenti e proposte per la celebrazione dell’Anno mariano, 54); Liturgy and pious exercises must co-exist in accordance with the hierarchy of values and the nature specific to both of these cultic expressions(Cf. Paul VI, Marialis Cultus 31, 48).
As I’ve said before in this series, the challenge is when the institution cannot provide clergy for the sacraments. What then?
74. Careful attention to these principles should lead to a real effort to harmonize, in so far as possible, pious exercises with the rhythm and demands of the Liturgy, thereby avoiding any “mixture or admixture of these two forms of piety”(Italian Episcopal Conference, Episcopal Commission for the Liturgy, pastoral note Il rinnovamento liturgico in Italia (23.9.1983) 18, in Enchiridion CEI, 3, Edizioni Dehoniane, Bologna 1986, p. 886). This in turn ensures that no hybrid, or confused forms emerge from mixing Liturgy and pious exercises, not that the latter, contrary to the mind of the Church, are eliminated, often leaving an unfilled void to the great detriment of the faithful(Cf. Marialis cultus, 31; Puebla, 915).
I can imagine that after long periods without the sacraments, faith communities might have some difficulty here and there when a priest is finally assigned, and the worship and piety already developed have to adapt.
Check the full document, the Directory on Popular Piety and the Liturgy, online at the Vatican site.