Things prophets haven't said

Traditionalist (and I number myself among them) often quote this:

We are what you once were.
We believe what you once believed.
We worship as you once worshipped.
If you were right then, we are right now.
If we are wrong now, you were wrong then.

But is it all that persuasive really?

There can't be many people who have difficulty conceding that they used to be wrong but that they're right now. If I were a modernist, and a traditionalist used that motto in a discussion with me, I'd probably respond, "Yes, I was wrong then. Now, I've seen the light!"

What might be a more persuasive argument?

Perhaps the fact that we have been warned to beware of novelties, in scripture for a start:

For there shall be a time, when they will not endure sound doctrine; but, according to their own desires, they will heap to themselves teachers, having itching ears: And will indeed turn away their hearing from the truth, but will be turned unto fables... - 2 Timothy 4:3-4

Notice the chronology. Truth first, being abandoned in favour of error. Not the other way round. 

In fact, I don't think I've ever seen any prediction that says that one day the Church will start getting things right after having been wrong for so long. Not that anyone has to believe in private revelations, but when none of them predicts that things are just going to keep getting better in the Church, it should make one think.

These days, I'm more interested in what prophecies don't say than what they do. Things like, "There will be a great Council, that will open the Church up to the influence of the world, and there will be a new springtime!" And, "The Church's liturgy will undergo immense improvements, allowing more participation by the people, and more involvement of women, who have been neglected for so long." Not forgetting, "Church buildings will be greatly improved by the removal of altar rails, statues, and the relocation of tabernacles to a less central position."

So on the one hand, we've had warnings that things will become very bad (a diabolical disorientation, as Sr Lucy put it), and on the other we've had no predictions that things will get better (except after a chastisement of some kind). Our Lady's Immaculate Heart will triumph eventually, but meanwhile there will be trouble.