I also read the first couple of Tarzan stories, and found insights such as that. Ayn Rand called it "bootleg Romanticism" the implicit creation of and attraction for art that depicts people acting on the basis of values. The 19th century was replete with this - and ERB another others of the early 20th century were, culturally, of the 19th century. The "Horatio Alger" stories are also typical of that time.

You can see a shift in the boys adventure stories. I have one from 1909 about a boy who runs away from home and learns to fly an airplane. … But a generation later, the Hardy Boys have an attorney for a father. They would never run away from home - can't work without a permit. And they have no insight into human nature.

Rand also cautioned against claims of "proto-Objectivism." We find examples of physical, intellectual, or moral heroism, and want to project Objectivism back onto them. We have to be careful about extending the context without reason to do so.

The great age of capitalism included such insights by implicit necessity. Capitalism and Romanticism could not have happened if the ideas were not known. The tragedy was that no one had identified and integrated them into a philosophy. But, then, Rand, was, as she suggested, either the last of their kind, or the first of their return.