According to karl marx, the working class in industrialized countries would remain poor and live near subsistence level. marx was right about the persistence of poverty in industrialized countries, but he was wrong in thinking that

Marx was wrong about the takeover of political power of the proletariat.

Even if poverty still exists in industrialized countries, the type of porverty that exists is very different from nineteenth century poverty. Poor people in advanced nations have access to all, or most basic needs such as food, clean drinking water, electricity, or heating.

Marx thought that poverty would persist in the same brutal conditions of the nineteenth century and that this would eventually lead to a proletariat revolution that would abolish capitalism. This did not necessarily happen even if many anti-capitalist revolutions took place in history, starting in 1917 in Russia.