Perhaps, but in my government the monarch himself appoints a competent successor rather than relying on eldest born or whoever the nobility thinks would be easiest to control. In this way we have had an almost unbroken line of good monarchs. Monarchs that aren't very good are killed in their sleep by the numerous Monarchist Nationalist organizations whose job it is to maintain the prestige of our dynasty. We DO have checks and balances, you just don't see them at the surface level of government.