> A large portion of our instincts are hard-wired.

Not accurate, or at least misleading. There's a lot of plasticity in the brain even at the very basic levels. Raising a kitten in an atypical environment (e.g., without edges or contrast), for instance, yields profound functional differences from retinal ganglion cells over V1/V2 up to the dorsal and ventral streams of the visual system.

We are what we are because our brains are hard-wired to adapt to typical environments. Full isolation would cause substantial aberrations -- that's exactly what you observe in real-world cases.