We know that the Church has an experience of two thousand years, and the human being is always inclined to a lack of discipline. The human being is always inclined to selfishness, to autonomy, to making oneself the boss of liturgy and prayer. This is human weakness, especially in the clergy. The clergy tend to want to present themselves as showman. This is a clerical sickness virus in all ages.
Therefore, Mother Church, as a good mother and pedagogue, established a fence of defense over the sanctuary and the holiness of the Mass, and also defended the simple faithful from the arbitrariness of the clergy and this clericalism by issuing strict rules. These are the rubrics commanding the clergy to observe strictly what is prescribed every moment of the Holy Mass. There is no gap. There is nothing void or empty. In the traditional form, everything is prescribed, and the priest had to observe it under the threat of punishment.
It was only for the sake of the glory of God, for the sake of the dignity of the liturgy, and for the dignity of the lay people, so that they would not be exposed to the evil clericalism of changing the liturgy and presenting oneself like a showman, like a clown. Now the Novus Ordo has so many gaps and voids, and it is written that the priest can change, can make this commentary, and the priest can speak with these or similar words. This is an open door for many unworthy comments and changes that celebrants are making all over the world. This must be corrected, of course.