I mean, capitalism is bad, but you're correct that my criticism isn't unique to capitalistic structures. Even anti-capitalist, radical collectives can suffer from bad "governance" (see The Tyranny of Structurelessness by Jo Freeman below for a wonderful analysis on the subject).
My experience has persuaded me that the statutory fiduciary duties of nonprofit boards have been, by convention/tradition, been assigned to executive leadership.
And to address your fear, an effective board would understand that their role is not to micromanage staff, but to direct the nonprofit so it can achieve its stated purpose by managing the executive leadership. The scopes are very different.