I think that endurance is an intrinsic limitation of drones, but I take the opposite conclusion as you. Instead of it meaning drones will never catch on, it'll mean that military missions and consequently the size and structure of the state will adjust their form to suit what drones are good at, rather than drones not catching on. In other words, we'll get drones, but we'll lose nation-states, rather than keeping nation-states but having them fail to adopt drones.

Drones' ability to absolutely dominate the battlefield inside of ~200km is just too powerful. You'll end up with small regional powers that are basically impregnable to invasion, but also can't project power because the range of drones is too short. City-states, basically. And because the defining characteristic of a state is its monopoly on physical force, the structure of the state will adapt to the dominant military technology of the time.