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By 1971 or so, Fr. Wathen dedicated his book, The Great Sacrilege: "To Pope Saint Pius V Guardian of the True Mass"
wherein he wrote extensively on the evils of the new mass utilizing Quo Primum as a reference often.

In 1974 Father Altenbach was another. One of his "True Mass tapes" was on Quo Primum.

St. Pius V did NOT establish the 1570 Roman Missal for all time. He would have neither that power nor authority since any action of the Roman Pontiff in liturgical matters can only extend to the Latin Church. (Antipope Bergoglio is currently treading into dangerous territory by involving himself in the liturgical matters of the Syro-Malabar Church, where he lacks competency and authority even if his opinon in this instance is accidentally correct.) A permanently binding act of a Roman Pontiff must pertain to doctrine and morals addressed to the universal Church. Liturgy is outside this domain.

Quo Primum, in fact, mandated missals older than 200 years, not merely permitted their continued use. The bull was an exercise of papal disciplinary power to eliminate the use of liturgical rites of questionable orthodoxy or orthopraxis that had emerged in the fifteenth and sixteenth centuries.

Quo Primum guarantees the use of the 1570 missal, but A new missal could introduced. In fact, half a dozen revised typical editions of the Roman Missal followed the of 1570. Each was clearly presenting Mass according to the received Roman Rite with nearly identical Ordo Missæ, but each had distinct rubrics and calendars.

The great problem with the Roman Missal promulgated by Paul VI in 1969 is that it is NOT the liturgy of the Roman Rite nor is it a distinct usage thereof. The Novus Ordo is in whole and in part an artificial and synthetic liturgy distinct from the Roman Rite yet masquerading as the Roman liturgy.

Too many trads over the past 50 years had had mistaken notions of the nature and authority of Quo Primum. Puts V guarantees the use of the classical Roman Missal as it had evolved down to the sixteenth century, but he does not nor cannot forbid something new and in continuity with the older form for the future.