Except the argument was it took everything they had to build the Crucible in that time frame. We're scrambling about sending "everyone who can hold a hammer" to Hackett. Diverting crucial resources away from "the only way to stop the Reapers" seems massively foolish.
It only seems that way because you haven't thought about the problem. All you're doing is feeling about it.
I guess I'll have to walk you through it. Let's do a simple version where Crucible success is simply pass/fail. We've got finite resources. We've got enough to do both a cheap version of the Crucible and an Ark, or a more-expensive version of the Crucible. We have a totally unknown required value for the Crucible to succeed.
We've got three possible states for the required success value.
Case 1: The required Crucible power is less than the cheap version of the Crucible. The Ark is irrelevant. We win.
Case 2: Required Crucible power is greater than the cheap option, but less than the expensive option. Building the Ark turns victory into mere survival.
Case 3: Required Crucible power is greater than our total resources. The Crucible is irrelevant; if we build the Ark we survive, otherwise not.
It's only in case 2 that building the Ark will be counterproductive. In case 3 not building the Ark is fatal. We don't need to think about case 1 since we automatically win. On the evidence available in the time-frame, you'd have to say that case 3 is pretty likely. How likely is case 2 ? Unless the Ark costs a fairly large percentage of the available resources, case 2 is unlikely to be the case, and therefore refusing to build an Ark is a very bad idea.
And obviously this ship is an established fact. I'm just pointing out it's looking less and less like a carefully-planned-out soft reboot and looking more and more like panicked flight from ME3's backlash.
No, I said that the Crucible was an established fact, so you can't make an outright impossibility argument. You can make an availabke-resources argument, but that fails as above.