Whilst not everyone has a good understanding of a wide range of complex topics (economics, diplomacy, medical science etc.) they have a very acute understanding

Whilst not everyone has a good understanding of a wide range of complex topics (economics, diplomacy, medical science etc.) they have a very acute understanding of their own best interests. Having a democracy ensures that policy makers at least have to convince people that something is in their best interests. Just because a policy maker is capable of convincing the public that something is in their best interests, does not always mean that it is. However the fact that they have to works enough of the time that democracy is working better than other systems of government so far by many measures.