I have read the Communist Manifesto. My take was that even Marx saw it as non sustainable (ah, that favorite word of the Left). He saw that it was necessary for the capitalists to build up the industries before the great confiscation, after which the “dictatorship of the proletariat “ would be lucky if they could just maintain status quo. Stalin did “expand” the economy in the USSR, by brute force and leaving a trail of ruin.
It was from the beginning an economic and social system that was doomed to failure.
I’ve read it a few times myself. It’s good to be familiar with the enemy.
I guess that is where religion or faith came in for Marx. Or maybe better said, philosophy. He thought his revolution would resolve the contradictions of previous social orders and create a new man and a new society that would be utopian. He wasn't looking at the economic details and nuances because he was so blinded by his own vision. He didn't even consider that the foundation of his view of history -- that human conflict was inevitable -- made the utopian dream impossible.