The problem, unfortunately, is there has never been anything other than a "scorched earth march to fully developed capitalist property relations" --anywhere, ever. Therefore, the issue becomes: is such a march historically progressive, despite the human toll? Marx, of course, answered in the affirmative in relation to pre-existing modes of development. You know all this.
I recommend that you read Theodor Shanin's "Late Marx", which makes a convincing case that Marx rejected the notion of universal models of development. Kautsky, of course, ignored the late Marx and reimposed this schema on Marxism. Lenin returned to the late Marx when he drafted the April Theses, which rejected the notion of a capitalist stage for Russia.
Marx wasn't around to witness the failed experiments to leap over the capitalist stage in both China and the USSR in the 20th century. I now think he may well have repudiated these efforts, especially on seeing the outcome, and interpreted the reversion to capitalism in each instance as consistent with his theory. He was not ammoral and would have condemned the massive social cost, but the moral dimension would have been subordinate to his analysis, and I expect also that he would have seen the Stalinist interlude as an effect rather than cause of these historical developments.
I see that you omit Cuba in this 2 sentence panorama of the last 100 years. Highly revealing.
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