"As an Orthodox Christian, I am free to ignore Paul VI's self-serving justification. He also was speaking without any benefit whatsoever of seeing the fruit of his works. Maybe the guy really believed all of that "infallibility of the ordinary Magisterium" stuff, and truly believed that it all had to turn out alright."
Apart from the fact that Paul VI's allocution here probably would not be viewed as part of the Ordinary & Universal Magisterium, I would agree with your above paragraph. Self-serving justification would seem a very apt way of putting it, although we have the benefit of hindsight, of course.
However, many Cardinals at the time, (notably Cardinal Heenan of Westminster) thought the radical innovations would do great damage, and so they proved to be right.
While I agree with you (and the then Cardinal Ratzinger) that liturgy cannot be fossilised and there is a natural (spiritual) process of gradual development, I would be interested to know how the Orthodox would view the idea of creating new Anaphoras or Eucharistic Prayers. Could you ever imagine an Orthodox Church creating a whole new Anaphora from scratch or would this just not be acceptable to the faithful?
Although the Roman Rite went through incremental changes from the 5th to 20th centuries, the Eucharistic Prayer was extremely stable for that 1,500 years (possibly longer) and it was commonly thought that this could never be changed - until 1969 that is! While Cardinal Ratzinger was probably thinking of the four main Eucharistic prayers we have as being a benefit of the N.O., I am sure he was not praising the situation that exists in France where there are now over 300 E.P.'s in use! Any sense of unity and coherence that might have remained in the N.O. in some countries was totally shattered in France by this ridiculous state of affairs. The variation is so bad that the French cannot even put a Missal together because the book would be too big and too expensive to use - most parishes there seem to work from loose-leaf folders or loose sheets of paper (not that their services are recognizable as Masses to most Englishmen anyway.)
To be honest, the idea is pretty unthinkable. The fundamental development that has taken place in the Anaphoras ended long, long ago. Our most recent anaphora -- that of the Liturgy of St. John Chysostom, is essentially an abbreviation of the Liturgy of St. Basil.
Not only the idea of change is pretty unthinkable, but also so is the idea of having a smorgasbord of choices in our liturgical services unthinkable. Give me a date in the future, any date, and with a little work, I could tell you exactly the prayers and hymns that would be chanted at the full cycle of all 9 services of the liturgical day (at least according to the Sabbaite Typikon followed by the Slavs and on Mt. Athos.)
Keep in mind that in most Orthodox parishes, most of the the anaphoral prayers are read quietly by the priest while the choir/chanters sing hymns of response and glorification. Only the clergy and altar-boys (and those who stand very close to the front, sometimes) can hear the full anaphora. The main exclamations are intoned prominently by the priest.
Some priests, primarily under the influence of the liturgical theology of Fr. Alexander Schmemann, do most of the anaphoral prayers out loud after the choir finishes each hymn.
I would be very happy to discourse at length on modern liturgical variations, and on organic liturgical growth and change in the Orthodox Church. We are anything but fossilized. But frankly, I can't imagine changing the basic text and structure of any of our services.