As the saying goes, when life gives you lemons, make a whiskey sour. To this extent, Traditionis Custodes may be a blessing in disguise in the long run. Let me explain.
Two things seem clear from the motu proprio. One, in fact, is clear. The Extraordinary Rite may now be celebrated only with the permission of the local bishop or only by certain religious communities (e.g., FSSP). The other is that Pope Francis sees the celebration of the EF as a sort of “up or down” acceptance of the “legitimacy” of Vatican II.
It is to this later point that, in the long run, there may be good news. No one can contest the “legitimacy” of Vatican II, just as no one can contest the “legitimacy” of Vatican I or any of the other twenty-one ecumenical councils of the Church. They happened. They are historical facts. In this respect, I could no more question them than I could question the “legitimacy” of the Missouri Compromise of 1820.