Vatican II had absolutely nothing to do with the New Order of the Mass. The revised Roman Missal was developed after the Council was closed. It was developed by a commission of experts, including some Protestant ministers, under cardinal Bugnini. The result was approved by Pope Pius VI and established as the new form of the Roman Rite. It is thus valid as long as the words of Consecration are observed.
Some argue that certain translations into the vernacular render the Mass invalid (ex. qui pro vobis et pro multis translated as “por todos los hombres” or “for all”), but these vernacular translations have been approved and therefore they are expected to be valid.
The old form was never juridically abrogated, and in principle was always permitted (cif. Summorum Pontificum, Benedict XVI). The Ordinary Form of the Roman Rite is as valid as the Extraordinary Form if celebrated according to the rubrics. However, sometimes the validity may be questioned when the words of consecration are altered, or if the priest does not intend to do what the Church does (which is very rare).
In general, the graces ex opere operantis may be said to be greater when the recipient of the Sacrament is more properly disposed - ex. where contrition, reverence, awe of the Lord, and interior recollection are greater.
It is erroneous to state that the Holy Spirit would not guide the Church to develop a new form which is inferior. All known heresies have sprung forth from priests, bishops, or religious of the Church. The very fact that liturgies such as the Holy Mass and the Divine Office had to be reformed time and again demonstrate that they indeed become inferior through time. The reform called forth by the Council in Sacrosanctum Concilium appear to have very little do do with the reforms (and indults) enacted and conceded in the following 40 years, which is why a large number of theologians, clergy, and laity have gathered to promote a “reform of the reform”, a restoration of the sense of the sacred, and the promotion of traditional elements of Catholicity called for by the Council such as the use of Latin in the liturgy, the Gregorian chant, and the pipe organ.
In general, one can define the Ordinary Form by the words of the Supreme Pontiff Benedict XVI in Summorum Pontificum:
in many places celebrations were not faithful to the prescriptions of the new Missal, but the latter actually was understood as authorizing or even requiring creativity, which frequently led to deformations of the liturgy which were hard to bear.
I am speaking from experience, since I too lived through that period with all its hopes and its confusion. And I have seen how arbitrary deformations of the liturgy caused deep pain to individuals totally rooted in the faith of the Church.
The most sure guarantee that the Missal of Paul VI can unite parish communities and be loved by them consists in its being celebrated with great reverence in harmony with the liturgical directives.
He also said other things as a cardinal, but those are not the official teaching of the Vicar of Christ requiring assent of mind and will. He said, for instance:
What happened after the Council was totally different: in the place of liturgy as the fruit of development came fabricated liturgy. We left the living process of growth and development to enter the realm of fabrication. There was no longer a desire to continue developing and maturing, as the centuries passed and so this was replaced - as if it were a technical production - with a construction.
The second great event at the beginning of my years in Regensburg was the publication of the Missal of Paul VI, which was accompanied by the almost total prohibition, after a transitional phase of only half a year, of using the missal we had had until then.
There is no doubt that this new missal in many respects brought with it a real improvement and enrichment; but setting it as a new construction over against what had grown historically, forbidding the results of this historical growth, thereby makes the liturgy appear to be no longer a living development but the product of erudite work and juridical authority; this has caused us enormous harm. For then the impression had to emerge that liturgy is something “made”, not something given in advance but something lying within our own power of decision. From this it also follows that we are not to recognise the scholars and the central authority alone as decision makers, but that in the end each and every “community” must provide itself with its own liturgy. When liturgy is self-made, however, then it can no longer give us what its proper gift should be: the encounter with the mystery that is not our own product but rather our origin and the source of our life.
A renewal of liturgical awareness, a liturgical reconciliation that again recognises the unity of the history of the liturgy and that understands Vatican II, not as a breach, but as a stage of development: these things are urgently needed for the life of the Church. I am convinced that the crisis in the Church that we are experiencing today is to a large extent due to the disintegration of the liturgy, which at times has even come to be conceived of etsi Deus non daretur: in that it is a matter of indifference whether or not God exists and whether or not He speaks to us and hears us.
When the community of faith, the world-wide unity of the Church and her history, and the mystery of the living Christ are no longer visible in the liturgy, where else, then, is the Church to become visible in her spiritual essence? Then the community is celebrating only itself, an activity that is utterly fruitless.
This is why we need a new Liturgical Movement, which will call to life the real heritage of the Second Vatican Council.