I can't think of anything that's more pseudoscience than the idea of instinct. I mean there's some parts that are obviously instinct or something just baked into whatever creatures: baby turtles running for ocean immediately after being born; generations of butterflies taking turns flying over and back between places; salmon, whatever they get up to. List goes on. And some creatures aren't much more than automata for sure. But there's so much else that sounds total bullshit. Social and solitary creatures for example. Polar bears living in conditions where food is incredibly scarce, forced apart for a chance at better hunting and because in hunger cannibalism is not unknown. Lions in the savannah, pushed together by all the other big monsters, elephants, crocodiles, hippos, other lions. Tigers solitary for no need of each other, kings of their jungle, their only competition being other tigers. All things that make a whole lot of sense. If you put humans in these animals' positions, we'd do the same of cleverness. But for the animals it's instinct. Then in captivity polar bears and tigers are plenty social. Some instincts.
We observed some crazy shit in nature and took an idea in it and applied it needlessly across the board. The idea also hinders adaptability massively.