Personally, I wouldn't go that far, I've found a decent number of managers to be value-adding. I think it is more about the sloppy mindset that tends to underplay the contribution of other producers on a team, to instead heavily over-value their own contributions. Engineers can go too far in this way too, of course. Managers can produce strategy, operational efficiency, organizational support for ill-understood projects, elevate performers, eliminate underperformers etc.