It's always weird to me to hear people talk about "democracy" as an abstract moral philosophy or a system of government. It sounds to me like people talking about "hammerism" or something, like the Builder faction from the Thief series.
There are many, many faults of democratic methods. But, let it be succinctly said: human beings are easily manipulated on short time scales. Anything left to a decision of the "majority of the people" is easily influenced by propogandists. In a system that is based entirely on the tool of democracy, power is accumulated by those most adept at manipulation.
A robust system of government that protects liberty, dignity, and enables people to improve their quality of life, will include democratic processes, which are useful, but will also need to employ a variety of other governmental and moral decision making tools.