I think Molinism has been like a cancer in The Church, expanding and undermining even the most fundamental of doctrines (Original Sin, EENS, etc).
Or you could see it as having a Counter-Reformation effect, preventing a too-rigid Augustinianism ( boy, does that sound pompous ).
I think it's a red herring, this whole argument. It's something Catholic intellectuals like to do to sharpen their wits. But the question is not resolvable, in my view. There are problems with every schema that you can come up with on grace vs. free will. The problem with Molinism is that it posits what I imagine like a giant invisible pool of grace that we just have to reach up and grab some of, as if it were an apple hanging from a tree. Any of us can have it, just as any of us can have air, as long as we choose to breathe. It's sloppy, sort of like my mixed metaphors in this paragraph.
If Molinism is unsatisfactory from the point of view of God's predestination, Thomism is unsatisfactory from the point of view of our free will. It also makes the idea that God wants all men to be saved an in-name-only proposition. The will has to correspond with sufficient grace, but God already knows whose will is going to respond, so that He can give them more grace ( efficient grace ). Yet if the will responds in the first place, it can only be because of grace, because of what He gives. So you enter this Catch-22. The sufficient grace of Thomism is actually often insufficient!
It makes you wonder, "Then why doesn't He give sufficient grace to everyone, so that their sufficent grace becomes efficient grace through a motion of the will? Why is this sufficient grace only sufficient for some and not for others, when it is God who controls how much grace is necessary for each person?" Couldn't this lead to the conclusion that God Himself is responsible for not giving enough grace to certain people?
So yeah, if you are going to be a Thomist, you flirt with the idea that God intended for some to be damned. And how does this square with His desire for universal salvation? Yes, He has favorites, but He still desires the salvation of all. Molinism resolves this problem, and its sufficient grace really is sufficient in all cases. That is the virtue of Molinism, that is the "Eureka!" aspect of it. It's just kind of sloppy, with grace being poured out all over the place indiscriminately.
Liguori had an in-between view, I forget the name of it, but that is what I have.