That's not it. QM provides the pots and pans and the kitchen to cook up a theory, but you have to bring the different ingredients for each type of interaction. The Dirac equation describes the behavior of electrons, and Dirac bragged that it "explains all of chemistry and most of physics". Of course the equation only has meaning in terms of the matrices, operators, and other apparatus of QM.
Today's particle physics depends on the "Standard Model" largely developed in the 1950's through the 1970's. Frankly most of it is beyond my ken, but it also is formulated in the context of QM. It is this "Standard Model" which might be the more worthy focus of your scorn.
To add my own 2 cents. My immediate thought was that this increase in meson production, were it to be amplified as they go to higher energies, could constitute an impenetrable fog which brings all their high hopes and expectations to naught.
Yeah, I thought about that too. But then you can learn a lot from even a null experiment. How you explain it to the taxpayer is another question.
I don’t know how you separate QM from the Standard Model, though. Obviously, the thing that went wrong here was their calculation of the probabilities. That methodology is provided by QM. If you constantly find something else to blame for the failure of the predictions besides QM, then of course you’ll never find fault with QM.