It's never the fly, it's always the fishing that takes the fish. Even in the situation of matching hatches, being in the right ballpark is all that matters.
Different flies may have different qualities that affect your ability to present them properly, though more often, adjusting line and leader addresses those differences.
In the case of wildest genetic rainbows - Alaska - put my buddy on the Russian River Ferry sockeye run to get it out of his system, and I was fishing beadhead nymphs for the native rainbows. Decided after awhile to switch to a sockeye-snagging rig with bare red Gamakatsu hook, and was catching more Kenai rainbows on the bare red hook than on the beadhead nymphs - even on the swing. It can be explained that even early July, they were already queuing on bits of salmon flesh (and we were down from the cleaning stand). But not a complicated pattern...a bare red hook.
We figure summer on the Guadalupe, someone needs to try a cheetos fly