This sacred Council has several aims in view: it desires to impart an ever increasing vigor to the Christian life of the faithful; to adapt more suitably to the needs of our own times those institutions which are subject to change; to foster whatever can promote union among all who believe in Christ; to strengthen whatever can help to call the whole of mankind into the household of the Church. The Council therefore sees particularly cogent reasons for undertaking the reform and promotion of the liturgy.
A common modern rhetorical tactic, when presented with argument X, is to refuse to engage with the argument itself and instead to dispute that the question which argument X addresses is in any way material or relevant, and thus to paint the one promoting argument X as a cracked-out marginal obsessive. This is, I suspect, a means of both disarming an argument one is powerless to refute while inoculating one’s own position against criticism by imbuing it with the finality of conventional wisdom.
If you troll, say, a discussion on the liturgy at Catholic Answers Forum long enough, you’ll hear that tactic put into use, with a refrain that goes something like this: “Why are you so hung up about liturgy? How we worship doesn’t matter. Christ is all that matters.” Note the hubris implicit in appropriating for oneself, against the consensus of generations of saints and martyrs, the authority to decide what does and doesn’t “matter.” Note too the mincing minimalism that sees liturgy as something extraneous to theophily rather than a logical fulfillment or development of it. One might as well say that the love a man shows for his wife doesn’t matter, all that matters is the love in his heart; or that the fingers on a man’s hand are somehow irrelevant to his humanity, so he’s just as well off without them.
In fact, liturgy does matter, and even the reformers knew this, as Sacrosanctum Concilium itself makes clear. Liturgy touches on everything: it is the place where the Church interfaces most visibly with the world, and the place where the Church’s invisible, mystical nature most clearly converges with its visible, institutional nature. It is a moment of theophany, of encounter with the Word Incarnate, and it is very possible for the structure of the liturgy either to facilitate that encounter and enable it to bear fruit or else to impede it and make it useless. The Council argued that the old liturgy had become an impediment to apprehending and living the Christian faith, hence a reform was necessary. Thus, implicit in the Council’s stated desire to increase the vigor of Christian life, promote Christian unity, and adapt the life of the Church to the needs of modern times, is a criticism of the liturgy as it existed up to that point — the claim that it did not invigorate the faithful, was an impediment to Christian unity, and was a relic unsuited to modern sensibilities.
These are real criticisms, and they may be accurate or they may be inaccurate, but the point is that they are allowed to be made. I would (and will) argue that the Council made the wrong judgment about the Mass, but I cannot argue that they were wrong to think they could make such a judgment.