Canon 1245 provides this faculty for pastors and others. It is also typically given to parochial vicars: “With due regard for the right of diocesan bishops which is mentioned in can. 87, for a just reason and in accord with the prescriptions of the diocesan bishop, the pastor in individual cases can dispense from the obligation to observe a feast day or a day of penance; or he can commute it to other pious works; the superior of a religious institute or a society of apostolic life of pontifical right if they are clerical can also do the same for his own subjects and others staying in his house day and night.”
In our diocese deacons also have this faculty by delegation.
While no one is bound to the impossible (* see below), the faculty allows better pastoral care for the troubled in conscience or the scrupulous.
PS, don’t let the English term “feast day” up there throw you. Sunday is the primordial feast day (canon 1246 §1, “primordialis dies festus”).
*Canon 1247: “On Sundays and other holy days of obligation the faithful are bound to participate in the Mass . . .”
*Canon 1248 §2 “If because of lack of a sacred minister or for other grave cause participation in the celebration of the Eucharist is impossible, it is specially recommended that the faithful take part in the liturgy of the word if it is celebrated in the parish church or in another sacred place according to the prescriptions of the diocesan bishop, or engage in prayer for an appropriate amount of time personally or in a family or, as occasion offers, in groups of families.”