John seems to be particularly calling out that he was not able to influence the people with high enough rank to make decisions. So it sounds like he at least thought there was an authority structure there wasn't as flat as you describe.
The upside is that people, in theory, don't need to wait to be promoted to (attempt to) have an outsized influence on what actually happens on their team, in their org, etc. The downside is that the "real" power/influence structure can be a more nebulous/social game, rather than something concrete that is diagrammed out in a visible org structure. It was often said at Google that you get promoted to level X after already doing work at that level, which implies that the people with influence are running around influencing/leading before they've been anointed with an official title that "gives" them authority.
Reading Carmack's letter, it sounds like he consciously chose to prioritize his personal programming/engineering work over his social/influence/leadership at Facebook. In all my observations, past a certain level, you kinda have to choose one or the other. Both are valid choices.
A lot of millennials value freedom of choice and open collaboration ad nauseam, but this is the danger of too many voices—nothing gets done. No singular purpose. No authority—or rather, no respect for authority. The reality is: we are not all equal. Some people are just better at what they do than others. Perhaps we should listen to what they say?
But that’s how politics goes—some schmucks who have no idea nor vision, nor experience, nor know-how, rise up on the backs of engineers who do all the work. Typically out of insecurity or over-ambition they trample on-up.
And who would want to deal with the cutthroat bullshit of trying to deal with these people?
Go Carmack—create something amazing with your startup. Meta will rot away in the next ten years because someone else will invent a better VR headset. Just like Linus helped invent a better OS—free to use, open to collaborate, with vision and focus. With attention-to-detail and quality-engineering as a first-class citizen.
It never is. In the absence of formal authority, people will unconsciously build an ad hoc structure on their own.
Kinda what happened to communism in Russia, if you think about it
I would argue it does work in practise, at least with a higher success rate than a formal authority hierarchy.