I know it's nice to gripe about management being dumb, but my managers at Facebook and Amazon were the opposite. I often ran into managers who, after a 10 minute discussion would make key insights that I had not noticed.
to the second point, i dont think i had a single good manager the entire time, i had a lot. the only one that wasnt terrible was the one that phoned it in and didn't bother me and just let me work. i never reached out to a manager there for technical advice.
I assume it's a way of saying engineering is a tiny part of the organization.
Griping about the uselessness of management is precisely the kind of folk wisdom that gets passed around. It's fun to divide the world into do-ers and managers, both because it rights the uncomfortable social hierarchy and encourages action over in-action.