With the existence of two 'forms' of the Roman Rite, the amount of liturgical pluralism in the Church is increased. In terms of the number of rites and usages, the increase is insignificant: there are already masses of them. Even limiting ourselves to the Latin Church, there are more than a dozen authorised ones. Even excluding what are clearly 'non-Roman' rites - the Ambrosian and the Mozarabic - we have distinctive usages of the Roman Rite, such as the Dominican, Premonstratensian, Carthusian, Braga, and arguably Sarum, and now the Anglican Use. Other religious orders have more limited variations, but variations nonetheless. They add the name of their founder to the list of saints in the Confiteor ('our Holy Father St Benedict' etc.), they have their own feast days. Everything is approved by the competent authorities in Rome, of course.
Liturgical variety is not a problem. Get over it.
So why do so many people get worked up about the fact that the Traditional Mass does things differently from the church down the street?
As with so many things, the principles clearly reaffirmed by Vatican II have been turned on their heads after the Council. When the Council said that all legitimate rites should be preserved, that the Church has no wish to enforce uniformity, etc., in the 1960s and 1970s here was an almost complete flattening of those legitimate differences which used to add interest and richness to the liturgical life of Catholics. The Dominican Rite disappeared from Dominican parishes up and down the land, to give just one example: a totally unnecessary tragedy. Many distinctive customs of England and Wales disappeared too, including many local feasts.
At the same time a new attitude to the liturgy started to produce a degree and type of liturgical variety which can only be described as chaos. The bewildering number of options, coupled with anarchic liturgical abuses, have produced a situation in which Catholics have a range of liturgical alternatives, on a Sunday, which is actually very unhealthy. These are not different ancient traditions, at each of which one may experience theological insights nourished by the spirituality of a great religious order or region. No, they are different whims of celebrants and their 'liturgy committees', reflecting in some cases a complete ignorance of liturgical principles and a contemptuous disregard for liturgical law. Is this the liturgical uniformity which liberal critics of the Traditional Mass, like Robert Mickens in the Tablet, want to insist on?
The Church's principle is:
Diversa, non adversa.