I do not agree with all interpretations of the quote but primed by:

That's not right. It's not even wrong. -- Wolfgang Pauli

I interpreted it charitably with "critical" loosely implying "worth thinking about" in contrast to vague ideas that are not even wrong. Furthermore, from thefreedictionary.com definition of critical, "1. Inclined to judge severely and find fault.", vague statements may be considered useless and so judged severely but much of the time they are also slippery in that they must be broken down into precise disjoint "meaning sets" where faults can be found. So vague ideas cannot necessarily be criticized directly in the fault finding sense. (Wide concepts that have useful delimitations in contrast to arbitrary ill-formed vague ones can be useful and are a powerful tool in generalization. In informal contexts these two meanings of vague overlap).