I am not so sure of this. The pre-Vatican II Mass was largely the same for over ten centuries. You are correct in saying that
the Mass itself was only 400 years old when it “ended”–but we all know Benedict’s Good News stomped that idea

–, as the Missal was standardized by Pius V in 1570, but it was just that, a standardization. Before 1570, each diocese usually had its own practices, but even most dioceses were very similar in practice. That is, diocese A was different from diocese B in how they celebrated Mass, but not by very much. The Canon of Mass (Roman Canon), for example, was exactly the same everywhere except perhaps a few "Amen"s. So to say that we “returned” to localized customs in the 1960’s is a misnomer, in my opinion, and a dreadful idea (whose reality is now being rectified!).
Yes, I have no doubt in my mind that people were excited for “the great big upcoming changes” that they were told about in the 1960’s. But this is what I, and not a few others, think: it is a generational thing. If you walk into an average parish nowadays, at least in the US of A, and mention “Vatican II,” you will inevitably get a very consistent result. The people who were alive before and through and perhaps right after (early 1970’s) the Council are the ones that get giddy and jump up and down. Strangely, no one under 40 really has such a reaction. So what do I mean by this? I mean that the reaction in the 1960’s was
over-inflated hype, that’s what I mean, not dissimilar to hype about a secular teen idol. What is my point in saying this? Certain people tend to
worship the
idea of what they think the Council said, making it an
idol, making it something it clearly is not nor was ever intended to be.