Why does adopting Marxism ALWAYS cause such misery and destruction (USSR, China, N. Korea, Venezuela)? Because Marx’s theories were wrong; they were at odds with the facts on planet Earth. The harder you try to cram a square peg into a round hole the more damage you do to both peg and hole.
At the root of Marxism is the Labor Theory of Value (the value of a product is derived from the amount of labor that went into making it). At the time Marx published his first volume, the Labor Theory had at least one gaping hole which was widely known (returns to capital are equal across the value chain, in contradiction to the labor theory). Shortly after Marx published his first volume, the labor theory was utterly destroyed by the Subjective Theory of Value, which is still in use today.
Despite having the rug pulled from under him, Marx went on to publish a second volume, which contained some obvious omissions. Marx promised to fill in the blanks in his next volume, which never came.
Bad enough that Marx carried on with a completely debunked foundation. Worse, Lenin and his ilk implemented this flawed theory to the tragic detriment of millions. Ideas have consequences…