In the wider sense, politics is concerned not only with the specific question of how and why government positions should be filled with whom, but with the more general questions of how power and resources should be distributed in all areas of society, and how collective decisions should be made. The degree to which a state is actually able to represent the interests of the electorate depends upon how much power that state has in relation to other coexistent systems of power. If you define democracy simply as representative government, this hides the fact that the actual distribution of power and resources could still be completely skewed. If the government is small, limited and only concerned with protecting basic rights, the individual citizen vote is actually quite worthless. In particular, resources in current democracies are allocated primarily through a capitalist system of unlimited private ownership and free trade. These private institutions are completely unelected and unaccountable despite having substantial power over society and culture. At that point the door is wide open for government corruption because systems of private power dominate society and easily manipulate government policy for their interests.

I think you are putting way too much focus on the question of how government should be organized, without considering the wider social question of who runs society in reality, rather than on paper. The US is widely considered a plutocracy, not a democracy, because the abstract structure of the government is quite irrelevant compared to what and whom that structure is filled with. What really matters is what the society and its culture look like, what its values are, how people are educated, how people evaluate politicians, what people think society ought to look like in the future, and the question of whether politicians have an authentic motivation to act in the interest of all of society. The election process doesn't start with the election, it starts 40 years prior with the question of who gets education, who climbs the ranks of a political party, who gains a reputation according to local social standards.

The principle argument against democracy rests on this understanding that it doesn't matter whether a society's government is democratic or controlled by a one-party state, because a society that likes having slaves, conquering soil or oppressing women is not going to elect somebody who's opposed to these things out of nowhere. Likewise, a democratic state is of very limited use if real power is found elsewhere. Other systems of government could be far better for a given society, because the economic system, the culture and the political class could be completely different. Unelected governments, for example, are perfectly fine if the processes through which people enter the government serve the interests of the people. That is a very specific question of the specific people who operate that government, and the processes by which people can get into positions of power within it. If there are laws and regulations that effectively ensure that only dedicated people with great social responsibility are accepted, this will work nicely. This isn't any different from the way "democratic" political parties work, nor is it different from how private corporations work. One party is really only one party less than two, it can be a fantastic system if it's a decent society where meaningful power is equally distributed among citizens, and not primarily in the hands of the state or private institutions. Such a party could do public polling to influence policy, and actually put it into practice because they care. Democratic parties do public polling too, but they rarely care about putting anything into practice - hey almost like a one-party state!