I don't see how that could be the case. If no change has occurred, then what can they be denying?
The changes that they and "Catholic" liberals falsely believe to have been decreed.
The changes that they and "Catholic" liberals falsely believe to have been decreed.
If I am understanding you correctly in what you are saying here I still would not be very clear on what heretical error could be placed at the feet of the SSPX. If that body thinks that the Council promoted something innovative and wrong, but the council didn't really do that, that doesn't quite seem to deserve the response or treatment they are currently getting. The pope could simply say "No, we don't believe that or do that, and what you do and believe is certainly just fine." If the council didn't change the faith then there is really nothing to correct as regards the SSPX, but rather the real danger would be the 99% of Catholic priests and bishops who teach that the council actually did make those changes to the faith and in turn enforce them on parishes throughout the world. The SSPX may be wrong in confusing the actions and opinions of the 99% with dogma, but in a practical sense you cannot blame them. Actions do speak louder than words, and Rome has never, to my knowledge, corrected any of those errors.
BTW, in the above I refer to heresy as the SSPX are regularly held up as deserving to be removed or kept out of the Body of Christ for their positions, and that would seem to require something of that kind for such a response to be appropriate. I may be wrong in that though as I can actually not think of any heretics, regardless of how dangerous, notorious or scandalous, which the Church feels deserve such treatment (outside of groups like the SSPX of course). When Fellay is a threat to the faith but Richard McBrien isn't I can honestly say I must not understand anything at all.
“The changes that they and “Catholic” liberals falsely believe to have been decreed.”
They may not have been decreed, but they are being taught and practiced. SSPX, like William F. Buckley, stands athwart history shouting “stop.”
Without SSPX there would be no indult allowing bishops to permit the Tridentine Mass.
I am not affiliated with SSPX, but I see among their critics the same malice and dishonesty that I see among the partisans of Barack Kardashian.