But it would be too credulous and not think anything through in enough detail to make sure it's right.

That's the problem with holistic decisions as described.

I'm not entirely sure I'm willing to follow McGilchrist as far as he wants to go with the left/right thing, but even if I follow him all the way, we really do need both types of thinking. And I think errors of both sort--holistic answers when a focus on principles is needed, and principled answers that miss the big picture--are quite common.

Covid and climate change are both great examples of areas where you need both: they're complicated, and it's easy to be mislead by wishful thinking unless you really focus on the topic so you'd better keep your holism at bay until you actually understand what you're synthesizing; but they both have broad implications so you do need to get to the holistic version before you start making policy recommendations.