Why do people hate capitalism?

Because it is seen as helping the rich become richer and poor become poorer and at disadvantage, and since it is the most dominant economic system in the world, it doesn't work perfectly well especially in poor and undeveloped countries. whatever system is perceived as unfair, or unjust will be hated.

Economically speaking the biggest point would be the Diminishing marginal utility of wealth. A capitalist society argues it is good if people can earn more leading to income and wealth inequality. However, this ignores the diminishing marginal utility of wealth. A millionaire who gets an extra million sees little increase in economic welfare, but that £1 million spent on health care would provide a much bigger increase in social welfare.

i believe capitalism's biggest issue is unregulated greed. resources are quickly captured by the wealthy because the system rewards are in their favour. worse still is that the resources would never be used for the greater good unless the capitalist is expecting a handsome profit.