Marx didn't have a solution, even socialism/communism wasn't a solution it was a prediction. In the cases of the Soviet Union and the other Eastern block attempts at communism, they were forced attempts, Marx's criteria for the success of socialism and ultimately communism had not been met. Hence they were doomed to fail from the start.
Oddly he was pretty ambivalent about mixed systems which most of us see as the solution to avoid end game capitalism.
But what of the even more distant future? Provided we aren't eliminated by an unlivable planet? Classic Marxism might provide the answer in that mixed systems would naturally evolve into socialism and ultimately a communism where machines do the heavy lifting and people have everything they want and need and generally do as they please.
A utopian pastoral society where war, hunger, and ill health are all things of the past. A society made up of artisans, poets, musicians, philosophers, farmers, fishermen, scholars and educators. A world where men and women can pursue whatever interests them without being forced to work for wages or for bourgeois overlords getting rich from their labor while they struggle to survive...
Some would likely have more than others, but it would be by choice as none would want for anything.
Good coffee, good weed, and time on my hands...