The 1962 Missal is 2000 years old?
From time immemorial the ecclesiastical hierarchy has exercised this right in matters liturgical. It has organized and regulated divine worship, enriching it constantly with new splendor and beauty, to the glory of God and the spiritual profit of Christians. What is more, it has not been slow - keeping the substance of the Mass and sacraments carefully intact - to modify what it deemed not altogether fitting, and to add what appeared more likely to increase the honor paid to Jesus Christ and the august Trinity, and to instruct and stimulate the Christian people to greater advantage.The sacred liturgy does, in fact, include divine as well as human elements. The former, instituted as they have been by God, cannot be changed in any way by men. But the human components admit of various modifications, as the needs of the age, circumstance and the good of souls may require, and as the ecclesiastical hierarchy, under guidance of the Holy Spirit, may have authorized. This will explain the marvelous variety of Eastern and Western rites. Here is the reason for the gradual addition, through successive development, of particular religious customs and practices of piety only faintly discernible in earlier times. Hence likewise it happens from time to time that certain devotions long since forgotten are revived and practiced anew. All these developments attest the abiding life of the immaculate Spouse of Jesus Christ through these many centuries ... Private individuals, therefore, even though they be clerics, may not be left to decide for themselves in these holy and venerable matters ... the sacred liturgy, as We have said, is entirely subject to the discretion and approval of the Holy See ... No more can any Catholic in his right senses repudiate existing legislation of the Church to revert to prescriptions based on the earliest sources of canon law. Just as obviously unwise and mistaken is the zeal of one who in matters liturgical would go back to the rites and usage of antiquity, discarding the new patterns introduced by disposition of divine Providence to meet the changes of circumstances and situation. (Pius XII, Mediator Dei 49-50,58,60,63)
Of course, for Lefebvrists, divine Providence no longer oversees the Church: "Rome would remain far from the Tradition. And it would be the end of the Church ... his ideas are heretical ... and they lead to heresy ... it seems that the Holy Spirit has taken a vacation" (Msgr. Lefebvre, qtd. in 30 Days, 1988, July/August).
No, but the lex credendi results from the Missal's lex orandi - which is 2k years old.
But don't neglect this part:
The Church is without question a living organism, and as an organism, in respect of the sacred liturgy also, she grows, matures, develops, adapts and accommodates herself to temporal needs and circumstances, provided only that the integrity of her doctrine be safeguarded. This notwithstanding, the temerity and daring of those who introduce novel liturgical practices, or call for the revival of obsolete rites out of harmony with prevailing laws and rubrics, deserve severe reproof. It has pained Us grievously to note, Venerable Brethren, that such innovations are actually being introduced, not merely in minor details but in matters of major importance as well. We instance, in point of fact, those who make use of the vernacular in the celebration of the august eucharistic sacrifice; those who transfer certain feast-days -- which have been appointed and established after mature deliberation -- to other dates; those, finally, who delete from the prayerbooks approved for public use the sacred texts of the Old Testament, deeming them little suited and inopportune for modern times.........Thus, to cite some instances, one would be straying from the straight path were he to wish the altar restored to its primitive tableform; were he to want black excluded as a color for the liturgical vestments; were he to forbid the use of sacred images and statues in Churches; were he to order the crucifix so designed that the divine Redeemer's body shows no trace of His cruel sufferings; and lastly were he to disdain and reject polyphonic music
"But the human components admit of various modifications, as the needs of the age, circumstance and the good of souls may require, and as the ecclesiastical hierarchy, under guidance of the Holy Spirit, may have authorized."
Your citing Mediator Dei is typical of the deception used by the modernists who pretend that the Novus Ordo is little more than a "revision", a "reform", a "renewal". It is none of these. It is a totally new thing, a protestantizing Mass concocted to appeal to Protestants and to replace with ambiguous expressions whatever was distinctly Catholic. This would have outraged the preconciliar popes who never intended anything more than to sanction modest modifications of the liturgy according to contemporary needs. Pius XII in particular was not anticipating in his encyclical the utter destruction of the ancient Liturgy. It is disingenuous for you therefore to suggest he would have acknowledged or in any way have approved of the work of Bugnini's committee. In fact, there is little doubt he would have been horrified and repelled by the Novus Ordo.