>>1620635Constitutional Republics (effectively a monarchy with a few stop-gaps and a retard slider towards ochlocracy) tend to fare better with their tech trees than the monarchs, even if their societies are a little unruly. WWI is a good example of this where the technologically successful monarchies already had something resembling a Republic/Junta for a while and the more "direct rule"/aristocratic rule type setups got curbstomped even if they had loyal and happy peoples.
It's not specifically a monarchy thing, but more of a "the less rules stopping them, the better" where the will of the people is wiser than the monarch in the moment, but needs an "aristocracy among men" (republic) to consider the longterm ramifications of the will of the people to make sure the people aren't fucking themselves. The issues today are the same as in any system where the aristocracy pockets the wealth while tossing bread and circuses at the problem. Bread becomes prohibitively more expensive until you reach a breaking point where the problem is cheaper to solve than the bread, or the barbarian hordes have already sacked the capital.