I have explained previously why it is it failed: it was too successful too quickly. When European monarchs used the power of written communication and efficient transport to eliminate their traditional rivals for power—barons, abbeys and guilds—the result was an almost immediate flowering of wealth, technology, culture and philosophy. That flowering empowered other groups to step into the shoes of the displaced medieval trouble-makers.
The first lesson, then for future formalist rulers, is to be less easy-going and tolerant of opposition than predecessors such as Louis XIV or Charles I. Getting rid of the old mess does not buy you very much time at all if you permit the concept of shared power to survive.
But even with that knowledge, accidents happen. Formalism does not promise a Utopia of endless peace and prosperity. A new trick, like cryptographic weapon-locks, might work for a few decades, but contexts inevitably change and new threats arise. Some of them will be successfully resisted, and some will not. Two centuries of peace and prosperity would be a great achievement of any system. Of course, absolute monarchy in Western Europe did not manage anything close to that.
The real tragedy of modernity is not that the absolutism failed. It was likely to fail sooner or later, and it is a shame that it did not last longer, but not a tragedy. The tragedy is that in the process, the clumsy and ad-hoc propaganda of its opponents got enshrined as holy writ. And while systems of government almost inevitably fail, and yet can be restored, that was not inevitable, but a terrible fluke.
When new religions are born, the details of their doctrine are massively unpredictable. Of course, Gnon filters religions for viability, but that is dictated by a few macro-features, leaving enormous scope for random features to be picked up and carried on in the religion's germ line. Looking at something like Mormonism or Baha'ism, you are struck by the sheer weirdness of what is included, usually just because it was one guy's pet idea.
The burst of cultural exuberance triggered by the arrival of effective absolutist government produced a new religion with some pretty random beliefs about the nature of Man. That religion became entrenched, as successful religions do, and the history of the last two centuries has been the history of its random doctrines being gradually applied by its culturally dominant devotees, starting with the most realistic and practical, and by now concentrating on those that are left, the most bizarre and indefensible, such as the total malleability of human nature.
That is the problem with modernity. Yes, we have bad systems of government, but that is something that happens from time to time, and can be fixed. Yet for us it is not being fixed, because along with the bad systems of government we picked up something far more damaging and harder to cure: a bad religion.