That verse you quote is in regards to completely new revelations/doctrines that contradict what was already given. True popes have changed and suppressed liturgies before. Were the Holy Week changes bringing new doctrines? If he was wrong, than wouldn't Pius V be wrong when he suppressed other liturgies younger than 200 years old in the Latin Church with Quo Primum?
Popes have previously declares that Catholics cannot only abide by those things that have been infallibly declared or promulgated.
Absolutely the new Holy Week rites imported new doctrine, and in fact a whole new ecclesiology.
True popes have changed and suppressed liturgies before, yes, but have they ever suppressed them and replaced them with wholly fabricated novelties?
The Pian Holy Week is a Novus Ordo.