You sure about that? Try explaining the PD to an audience of undergraduates without getting mixed up or mixing them up.

Then explain why in a repeated game, the results can be completely different, and what strategy is optimal in a repeated game system.

Then explain why it all falls apart if the game ends at some known point. What if it ends but at an unknown point.

Then try to decide what game you are actually playing.

After that, then there is cooperative game theory to go through… …oh, and the Colonel Blotto game… or the games in which the optimal strategy is to randomize your decision so the opposing party can’t predict what you are going to do.

Game theory is more than just resolving the PD problem, even if that’s the most famous one. It’s just a set of tools for analyzing strategic situations. Yes, other people have analyzed some of them before, but not in the same systematic way. It’s a bit like saying that people knew about velocity before calculus, so what’s the big deal about derivatives (though I’ll concede that calculus has many more applications in general than game theory).