Some thinkers noticed the productive potential of capitalism, but none with the shrewdness of Marx, if you know any writer from that era that rivals Marx in his analysis of capitalism, then feel free to re-produce it, I would be more than happy to read their words myself. Even more importantly, Marx not only sees the immense productive capacity inherent in capitalist social relations, but at the same time, sees the destructive potential as well. Marx, understands that capitalism is heroically progressive, but at the same time a producer of unimaginable misery and barbarism. The triumph of Marx over other thinkers is that he manages to capture the dualism that is inseparable from capitalism.
The concept of exchange value, and labor value does not belong to Marx at all. It was David Ricardo's innovation. Marx though, took one step further, and explained the source profit, through the theory of "surplus value"
Marxist concepts (dialectics from Hegel, Logic from Aristotle, English political economy, French political theory, Feurbach's critique of ideology) are not original in themselves, what is original, is the way they are brought together in a systematic tour de force that forever changed the course of human history.
I wonder how you can claim with such certainty that Marx got the theory of value wrong. Like I said before, Marx's theory of value is not his own innovation, it is inspired from the Classical English political economists (mainly Adam Smith and David Ricardo) Those theories of value were widely accepted within pro-capitalist circles, until Marx himself appropriated them in a systematic thought that went against capitalist logic.
Your allegory with Aristotle, Newton and quantum physics sounds quite bizarre to me. Would you be willing to develop it?
You claim that language such as that employed by Karl Marx himself is typical of the early 19th century. If that is the case not many people seem to have noticed. Would you be so kind as to re-produce the texts where Charles Dickens and Victor Hugo speak in the dialectical manner of Marx and Engels regarding the capitalist mode of production?
In fact I would heavily disagree with you about modern Leftists. In fact the vast majority of Leftists, has long ago abandoned Marxism. That was the case in the period right before the Great War, and even more so, during the neo-liberal period, where all the Social-Democratic parties in Europe were desperate to distance themselves from the working-class and the like. They were arguing that they were for the so-called New Economy and blah, blah, blah.
And I do not see how the invention and existence of the Boeing 747 absolves, capitalism, the free market and free trade from all the horrors they inflict upon humanity every passing day. The Marxist hypothesis against capitalism, is not based on the assumption that it cannot carry technology forward (in fact Lenin himself says: "There is no technical challenge that capitalism cannot deal with) it is in fact based on the expectation that it cannot deal with the social problems that simply arise from its mere functioning.