If you are not a sedevacantist, then it is perfectly within the power of the Pope and Bishops (with his permission) to eliminate or move days of obligation. He's only being consistent. Whether you like it or not, this is just fact.
Being sedevacantist (or not) is a different matter.
Once you look at everything through the lens of "well, this is the Church, and they have the power of the keys..." the whole Traditional Movement collapses. The whole "resist" portion of "recognize and resist" collapses.
Tradition has always been about "pretending that Vatican II was just a bad dream" and crafting lifeboats, makeshift churches, in which we stick to the ENTIRE PACKAGE of what used to be Catholicism: all the old standards of morality, disciplines, liturgy, and spiritual practices. Heck, we still use the 1962 calendar (or earlier) as well as an outdated (1962 or earlier) Missale. We area also decades behind in terms of priestly formation (no TV, no modern philosophers, teaching Theology in Latin, no psychology course, no Freud, no sensitivity training, teaching seminarians animosity towards the Modern World, etc.)
Where does this neo-SSPX line of reasoning end? They're starting from "recognize" and pretty soon there won't be any "resist" left, because the official Church, with the power of the Keys
has instituted the New Mass, etc. so how can they oppose it any longer? Where do they draw the line and say, "We are Trad, we aren't going there." Today it's 2 miles away, tomorrow it's 1 mile away, and next year it will be just 100 feet away. Before long they'll be OK with the Novus Ordo Mass, merely "preferring" the Latin Mass (which is what they will soon start to call the Tridentine Mass).
It's a bunch of crap. The whole argument: namely, just because we fail to depose the Pope (or declare him deposed) we must go along with the destructive insanity
Traditional Catholics have not acted this way up till now.