Ethically, if you extend this reasoning, are we not obligated to find a position in the most morally repulsive organization we are aware of, and then coast?

yes, this is called 'effective altruism'

I think there is an implied "given the company you joined turns out to be nonethically aligned"

One could find a position in the most morally attractive organization they are aware of, and then work really hard.

well not coast, the intent is sabotage