True, the frivolous writer often uses a lot more monarchies, and is not quite aware of other possibilities. And their character of lowly birth often have an entirely too easy time talking to the king. Even people of quite high birth would have more difficulties getting to the king in reality.
But at least, they aren't out to change the political systems of their world. It's amazing.
If you want to have a revolution in your world, write down on a piece of paper: There Are Arguments Against Democracy.
And then find them out before you write. And use them. And don't make using them proof that a given character is evil.
After all, James Madison pointed out that democracies commonly had short lives and ended very bloodily. Someone who more seriously disproved of that form of government would have more arguments against it.
Not all the characters will, of course. The overwhelming majority, unless you chose your setting very carefully, will not be able to argue for monarchy -- any more than most people can argue for democracy nowadays. They, like us, will just take it for granted.
If you expose them to the concept of democracy, they will not instantly say, "How wonderful!" They are far more likely to say, "How appalling!" They very likely to fight quite hard against the notion -- and in the process, at least some of them will figure out the arguments.