Under present conditions, the Vatican’s reunion with the SSPX would reinforce the notion that doctrine is not about truth, but about power.
It would seem we have enough prelates who dissent with Church teaching for a smorgasbord of personal reasons. By utilizing the method of a personal prelature to allow the Lefebvrists to be in union with the Catholic Church without unity over Vatican II teachings is in effect condoning and validating dissent by the clergy without consequence. If this was possible in 1521 Diet of Worms, Luther would still be a Catholic Priest but running his own sect of Catholicism. That would have negated two of the four marks of the Church: One and Catholic. It would have and likely will through these types of deals denominationalize the Church.
It appears that like the word marriage, unity is being redefined to justify and promote any reunion. Did Paul accept the Judaizers who wanted to retain the Jewish customs while following Christ? Was he wrong by saying no and scolding Peter?