I don't see how that can be proved or disproved, it seems to be purely a matter of conjecture to me. There is a broad range of opinion on the effectiveness of Fed management.From what we can tell, America has been growing as well with the Fed as it did before. That's another way of saying that long range economic growth was just as good with the gold standard as it's been since those bean counter salaries at the Fed got added to our taxes.
There's more to it than that though.
Besides overall growth, we've also got to live with the year to year changes. and that's what the Fed's been able to change. Sure, nobody's completely eliminated economic cycles, but in this age the cycles are more like measles --less often and a lot less lethal than they were a hundred years ago.