Even if we were successful in building an Ark, the bloody thing would sink anyway. Or some plonka wouldn't like the design and would want to do a rebuild or put it back up on stumps.
It'd spend most of its time going backwards...or at the very least, the complete opposite way to which it should be going....all due to the lunatic in charge of the steering wheel.
Actually, dont think arks have rudders, or steering wheels?...they just bob around and hope they'll get to where they are going....
And, as for filling the Ark up with ' the right types ', its construction would be so flimsy that few would want to take the risk and 'jump on board', and those that did would be just coming along for a free ride anyway...
Still, The Great Purple Ark would be attractive to some poor mongrels and long suffering fools who'd happily 'jump on board' thinking that the mighty vessel had half a chance of providing a leisurable, pleasant journey, and that it was indeed going end up at a destination very purple and very attractive, after the flooded world beneath had been ' cleansed'.
The poor sods!
So, yep God, just 'send it down', save us all the bother, and put us out of our misery.