high standarts of living and low levels of corruption — neither of which would be possible under an authoritarian regime

that's not always true, just usually. It's possible to "stagnate" standards of living pretty easily if they are already high. That's not to say that capitalism doesn't have it's place, but I'm just pointing out that managed flatlining is a thing (see Japan).

As far as corruption being inevitable for authoritarianism, I'd challenge that too. It's certainly the almost entirely likely scenario because most philosophical precepts that get one to authoritarianism start out wrong and therefore stay wrong further on. But when starting out righteously, it could be possible to maintain with extreme transparency and enforced honesty. Basically I'm saying that the decay isn't inevitable. But it will bring to the forefront any problems that were already there under less rigid systems, like how communism shows the faults that already existed under the more 'happy' socialist systems that would have taken far longer to destroy those societies without course-correction.