Believers are called to the imitation of Christ, but in MD 82, Pope Pius wishes to make clear this does not give non-clergy the “power” given to those who are ordained.
81. It is quite true that Christ is a priest; but He is a priest not for Himself but for us, when in the name of the whole human race He offers our prayers and religious homage to the eternal Father; He is also a victim and for us since He substitutes Himself for sinful (humanity). Now the exhortation of the Apostle, “Let this mind be in you which was also in Christ Jesus,” requires that all Christians should possess, as far as is humanly possible, the same dispositions as those which the divine Redeemer had when He offered Himself in sacrifice: that is to say, they should in a humble attitude of mind, pay adoration, honor, praise and thanksgiving to the supreme majesty of God. Moreover, it means that they must assume to some extent the character of a victim, that they deny themselves as the Gospel commands, that freely and of their own accord they do penance and that each detests and satisfies for (their) sins. It means, in a word, that we must all undergo with Christ a mystical death on the cross so that we can apply to ourselves the words of St. Paul, “With Christ I am nailed to the cross.”[Gal. 2:19]
82. The fact, however, that the faithful participate in the eucharistic sacrifice does not mean that they also are endowed with priestly power. It is very necessary that you make this quite clear to your flocks.