Here is David Friedman writing in 1973.
Much of the opposition to institutions of private property comes from popular beliefs about the effects such institutions have had in the past, beliefs largely unsupported by historical evidence. Marx was scientist enough to make predictions about the future that could be proved or disproved. Unfortunately, Marxists continue to believe his theory long after his predictions have been proved false. One of Marx's predictions was that the rich would get richer and the poor, poorer, with the middle class gradually being wiped out and the laboring class becoming impoverished. In historical capitalist societies the trend has been almost the exact reverse.
Friedman goes on to offer the (at the time) left wing explanation for the success of capitalism in the US:
Many modern liberals argue that Marx's predictions were accurate enough for laissez-faire capitalism, but that such liberal institutions as strong labor unions, minimum wage laws, and progressive income taxes prevented them from being realized.
Of course Friedman rejects that explanation, but since he wrote this labor unions have been severely weakened, minimum wage is now the lowest (in real terms) that it has been in half a century, and the tax code has become much less progressive. These are all shifts to a more laissez-faire capitalism. Seems to me that Marx' predictions were accurate.