In the film Jurassic Park, a 12-year-old girl has to use the park’s security system to keep everyone from being eaten by dinosaurs. She walks up to the control terminal and utters the immortal words, “This is a Unix system. I know this.” And proceeds to (temporarily) save the day.
Leaving aside the plausibility of a 12-year-old knowing Unix, simply knowing Unix is not enough to immediately use any application running on the system. Yes, she could probably have used vi on the security terminal. But the specialized security system would have required some learning time — significant learning time if it were built on Unix, which has notoriously inconsistent user interface design and thus makes it harder to transfer skills from one application to the next.