The problem is more one of impersonal, emergent, bureaucratic forces. Any particular officer, defense contractor, politician, pentagon analysist, etc ... might want to change how the system as a whole runs. But they are other groups (who might even agree with the overall goal) that will oppose any particular change that impacts their own political/bureaucratic/social power or influence. The result is an institutional inertia where only changes that fit into certain well-tread paths can succeed. Solving this collective-action problem is one of the major challenges of our era in many different verticals.

This relates to one of Hemingway's famous lines, "Gradually, then suddenly." When this a mismatch between the collective desires of a large group and their current circumstance, when suddenly there is some sort meaningful change (a disaster, a drastic court-case, assignation, etc ...) all of sudden rapid change can ensue.

I'd be really interested to know what could change the US Military-Industrial Complex. Our history of political changes and wars of the past hundred years seems to have been fluctuation on a common trajectory. It seems like we need something drastic, but the consequences of whatever is more drastic, seem large enough that they could be far worse than the current status quo. But there has to be something, I'm not trying to fatalistic here.

Yes, because when you read about the great failures of the U.S. military for the last 100 years, it usually boils down to political reasons rather than a failure of military planning. For example, the U.S. military understood vietnam and afganistan to be unwinnable years before politicians were willing to admit as much in front of the American public. The stunts in central america were all dictated by politicians for political reasons as well, mostly in effort to protect American corporate interests who had their assets seized by communist governments.