Once you've removed managers, there aren't many non-productive people left to fire.
A gaggle of developers are not going to be able to do this. Hell, 50% don't even have the social skills to say hello to each other in the morning.
Vetting hires for temperament and internal qualities as well as skills makes this much more possible.
That is only true if you hire folks that aren't self-motivated, driven and talented.
This nirvana of extreme self-motivation at all costs you seem to espouse is not a reality for most people on the planet. It is most likely a privilege.