In Asimov's "Foundation" humans had flown and fought in space for one hundred thousand years, and they STILL use two-dimensional tactics! And it's not an oversight on Asimov's part -- when Bel Riose wins a major battle by utilizing third dimension, the losing side accuses him of cheating. IOW, Asimov clearly thought of the matter, just his conclusion is flatly incredible.

I think Asimov always regarded vast majority of human beings as collectivist, tradition-bound, and unwilling to experiment. (Socially experiment, that is.) Which is not surprising for a Russian Jew who grew up in Brooklyn during Great Depression. There are few rugged individualists in immigrant tenements, and even fewer during Depression.

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Fiction has to be plausible. Reality is under no such constraint.