Marx is often accused (ever since Bernstein and the revisionist
Marxists of early 20th century Germany) of neglecting the fact
that a democratic proletariat could simply vote to mitigate
their living conditions, but that's not really where he went
awry. What he thought was that as productivity increased, an
ever-smaller workforce could produce enough stuff to meet
aggregate world demand, leading to ever-increasing unemployment,
declining consumer power, falling wages, and an inevitable
economic collapse. Then what would happen is that we would
realize that we had all these capital goods lying around, all
these unemployed people, all these productive workers, and that
it would be easy enough to meet all of our needs by just
abolishing ownership and letting everyone do their own thing.
And, indeed, despite the claim that "Communism doesn't work" it
would actually be very easy for us to guarantee everyone a
standard of living that would be quite comfortable by mid-19th
century standards on an egalitarian basis.