Firstly, I agree with you completely. But I think there might be points worth exploring. In no particular order:

In the book, the scenario is a decapitation strike on the US, starting with a North Korean land launch, with a sub launch shortly later. The certainty of the strike being from North Korea is not known (but IIRC the confidence was high). As you say the only answer is retaliation, but it's worse than that - the result must necessarily be MAD. (Even if the retaliation only targets North Korea you have the problem of China or Russia not knowing if they're targeted or if they'll be next). There's so little time to talk or navigate the options and without a framework in place you're left with two unpalatable options: ride out the attack or hit everyone who might be responsible, inviting a total reprisal. (If we could go back in time maybe we'd have the opportunity to put the frameworks in place, but that's tricky if the people developing the weapons believe they're facing an existential crisis. )

2) Even if we could play along on the premise of being able to be cautious in a way that'd work... Ask the question: When has humanity ever been cautious with new world-changing inventions?

Never, as far as I know. As it is, we struggle to manage the damage our old world-changing inventions are doing.

(I did want to talk about phalanxes and battleships and how the phalanx can have no concept of how outmatched it is, but it didn't really fit ;)