Capitalism was an economic system based on ownership of the means of production by individuals competing in a free market. As the Doctor described it, "Some people win; most lose all they had." (AUDIO: The Emporium At The End)
Capitalism could be exploited to the extreme with no regard to the lives of others. Ganymede Systems began to not providing oxygen in space stations and forced people to buy it via smart suits. They also began killing workers when they hadn't been productive enough and brought into new workers. However, thanks to the Twelfth Doctor, a rebellion was started and Ganymede Systems was overthrown. (TV: Oxygen)
The Eighth Doctor was assumed to be a capitalist by several people in Spain. Fitz Kreiner branded Anji Kapoor a "capitalist pig" who was in turn surprised by how similar career communists and career capitalists were.
While fighting in the Spanish Civil War, Bob Edwards used a megaphone to shout out lengthy political arguments about the capitalist system. (PROSE: History 101)