Standing back and letting your gargantuan fleet do its best instead of messing with that AI when you have no idea what you're doing and nobody to advise you is a perfectly understandable choice of action.
But it's not presented as a possibility based on any in character perspective.
As I've said, building the Crucible and using it only makes sense if you've given up on any hope of conventional victory.
Point being, if we believe conventional victory is possible, why is Shepard bothering with a device whose functionality he has no understanding of?
Why does conventional victory suddenly become more plausible after we've launched everything into deploying the Crucible? Iakus hits on this above, but Hackett's dialogue prior to Shepard meeting the Catalyst is pretty indicative: "Nothing's happening" - so what was supposed to happen exactly?
Now that the Reapers have the Citadel, why do we believe we're going to beat them conventionally if and when they decided to shut down the whole network? There's nothing about the Refuse scenario that fits anything but the most insane character concept.
That is not a meta standpoint. Shepard knows nothing about the data or the Crucible's technology, but everyone who does believes that the Crucible can win us the war if we build it and use it right, enough for Hackett to commision and prioritize its construction on top of everything else. That's called listening to your experts. Again, it's not Shepard's call to build it or launch a suicide mission to activate it, it's Hackett's, and Shepard is following orders because it'd be ridiculous not to given expert opinions.
To be clear, do we have a source for this?
Not to mention, we need the "we can win this war conventionally" dialogue. Until we have that, Refuse is insanity, particularly once the suicide mission of deploying the Crucible is launched.
Iakus also hit on this, if your experts can't even figure out basic design operations, like how to turn the machine on, why are we buying into the "we can destroy the Reapers with this" premise? This gets more ridiculous once the Reapers have taken the Citadel because now, if we want to test drive the Crucible as some weapon, we now have to sacrifice our fleet just to get the Catalyst back. I'm serious here: none of this sets us up for a narrative where conventional victory is a possibility. It's not mentioned, it's not weighed as an option, it's not given any consideration whatsoever as any sort of back-up option.