Like, the Inca? They were building bridges and stuff out of rope, out of fiber, that Europeans just flat out could not figure out. Bridges made from plant fiber stretching between mountaintops across enormous valleys that you could ride horses across. Europe just did not have that level of prowess with fiber and rope.

One thing I love about Stellaris is that it's one of the very few 4X games (the only one I'm aware of, actually) that models this, albeit in a sci-fi context. There are certain technologies that you can't research normally and can only learn by studying pre-FTL civilizations. If you forcibly assimilate or kill those civilizations, then welp their culture is gone and the knowledge is lost forever.