Why did Karl Marx and Friedrich Engels believe capitalism harmed industrial workers?

Karl Marx and Friedrich Engels argued that capitalism was inherently harmful to industrial workers, or the proletariat, due to systemic exploitation and structural inequality. Their critique focused on several key factors:12

• Exploitation and Surplus Value: Marx maintained that all economic value is created by human labor. Under capitalism, workers are paid only a portion of the value they produce, while capitalists appropriate the remaining "surplus value" as profit. This process allows owners to amass wealth while workers remain in poverty.31
• Alienation: Marx identified that capitalism causes alienation, where workers become estranged from the products of their labor, the production process itself, their own creative potential, and their fellow human beings, whom they are forced to view as rivals.14
• Systemic Misery: Engels, in his observations of industrial life, highlighted that the poverty, disease, and early death experienced by workers were not accidental but endemic to the capitalist system.2
• Ideological Control: Marx argued that the ruling class uses ideology—including media, education, and religion—to justify inequality and foster "false consciousness," leading workers to accept their own exploitation.1