I would like to draw your attention to a very insightful post by Fr. Anthony Chadwick. He writes a tribute to the life and work of Dom Prosper Guéranger and lists what he considers twelve aspects of what Guéranger considered the anti-liturgical heresy:
1. The rejection of tradition and changing the liturgy to make it conform to doctrinal or theological principles or teaching.
2. Replacing texts composed by the Church by texts from the Scriptures. For example, the Introit Salve Sancta Parens in the Masses of Our Lady was abolished for this reason.
3. Composing new texts to replace biblical texts when it suited the purpose of making liturgy follow theology.
4. The illogical character of these changes: The desire to return to a primitive simplicity in the liturgy would become impossible when respect for the Tradition had been lost.
5. The desire to find a rational explanation for every liturgical action. This is just what is called pastoral pragmatism by Pope Benedict XVI, an excessive desire to simplify the liturgy, leading to a loss of the sense of mystery.
6. The “extinction of the quality of unction“. Here he means what we call the sense of the sacred. He found that the Jansenists were hostile to notions of “giddy piety” or “the blessed mutter of the Mass”.
7. The diminution of veneration of Our Lady and the Saints. The Sanctoral was severely pruned back in favour of the temporal cycle in some of the eighteenth century neo-Gallican missals.
8. The use of the vernacular language. Most of the Jansenist-reformed rites continued to be celebrated in Latin, like, for example, the Vintimille missal of the Archdiocese of Paris. The parish priest of Asnières, Jacques Jubé (1674-1745), favoured the vernacular as well as many other proposed reforms that inspired Bugnini in the twentieth century.
9. The desire to shorten the prayer of the Church: In the desire for simplicity and practical functionalism, the tendency was to shorten the lengthy and onerous parts of the liturgy.
10. The rejection of the authority of Rome: manifested in the elimination or alteration of prayers for the Pope or showing the primacy of Saint Peter.
11. A diminution of the dignity and role of the priesthood. As in the Pauline reforms after Vatican II, some Jansenists had very forward views about reducing the distance between the laity and the clergy. Many a fine rood screen thus disappeared!
12. The increase of secular control in ecclesiastical matters. I find it hard to see a form of ‘Erastianism’ manifested in the liturgy.
Fr. Chadwick then offers his own analysis of how so many reforms proposed in the 19th century that were shocking at the time are now consider commonplace, but not often to the benefit of the liturgical life of the Church.