5.1 Changing the Prescribed Texts of the Mass; Ad Libbing; Inclusive Language
All the texts of the Mass - prayers, responses, Epistles, Gospel - must be according to the norms approved by the Church. Under no circumstances can anything be changed outside of the rules laid down by the Church. This is clearly stated, even in Vatican II! The modernist usage of inclusive language is getting more widespread.
Sacrosanctum Concilium #22: (1) Regulation of the sacred liturgy depends solely on the authority of the Church, that is, on the Apostolic See, and, as laws may determine, on the bishop. (2) In virtue of power conceded by law, the regulation of the liturgy within certain defined limits belongs also to various kinds of bishops' conferences, legitimately established, with competence in given territories. (3) Therefore no other person, not even a priest, may add, remove, or change anything in the liturgy on his own authority.
Canon 928 The eucharistic celebration is to be carried out either in the Latin language or in another language, provided the liturgical texts have been lawfully approved.
Inaestimabile Donum #5. "Only the Eucharistic Prayers included in the Roman Missal or those that the Apostolic See has by law admitted, in the manner and within the limits laid down by the Holy See, are to be used. To modify the Eucharistic Prayers approved by the Church or to adopt others privately composed is a most serious abuse."
Be aware that it is possible to invalidate the Mass if the key words of the Eucharistic prayer are not properly performed as previously described. ("This is My Body" and "This is ... My Blood")