Some of the meetings I've had have had 10x impact on what any individual contributor would have done during that time, if the meeting didn't happen.

I think it's a fallacy to think of work this way. It doesn't really matter what % of your time you spend "working". What matters is the results you achieve. These can only be measured in periods longer than 1 day, so I wouldn't trust any recommendation or finding based on the answers of this question.