Even the classical economists like Smith and Ricardo thought that labor was the source of value, and Marx considered himself as following and building on their foundation. It was only later with the austrian-school economists like Mises, and Hayek that value moved from labor to become “whatever people get from trade” or “whatever gives you utility-points”, IE fake-magic-happy-points that could be created and destroyed at will.

Richard Wolff has a good intro article on the economics discipline serving as high priests of capitalism