Democracies are certainly capable of building infrastructure but they tend to be less agile than dictatorships since they can not just appropriate land and disown whomever they please. This is a good thing in times of peace and prosperity but it can be a hindrance in times of war.
China is not a capitalist country though, the system is closer to some form of fascism which is just one of the many forms of collectivism under which socialism and communism also reside. Fascism and socialism/communism are closely related through their reliance on central economic planning and the fact that they empower the state over the individual, it is mostly rhetoric which divides them. Socialism is the pre-stage to communism, the difference being that in a socialist state the means of production are owned by the state while the state is supposed to wither away under communism because it is no longer needed.
China is not a capitalist country though, the system is closer to some form of fascism which is just one of the many forms of collectivism under which socialism and communism also reside. Fascism and socialism/communism are closely related through their reliance on central economic planning and the fact that they empower the state over the individual, it is mostly rhetoric which divides them. Socialism is the pre-stage to communism, the difference being that in a socialist state the means of production are owned by the state while the state is supposed to wither away under communism because it is no longer needed.