I think you are misusing the word plenary, which is usually referred to in Pope’s rulings on indulgences, penances, fasting, etc.; not the abandonment of “the organic, living process of growth and development over centuries, and replaced it – as in a manufacturing process – with a fabrication, a banal on -the-spot product (Cardinal Joseph Ratzinger)”.
You are quoting my favorite. But, if plenary is wrong word, the absolute might be better. And yes, prudence in changing the Mass is ideal, but not mandated in any way as far as I understand it