You know when your boss goes "I don't get it, you're just welding metal. There are machines that can do this. Why does it take you a full day?" or "You're just adding a button to this program, why do you need meetings and designers and a week just to do this?" or "All you do is flip burgers. Why do you need to call in sick? Anyone can do this job." That's pretty much what you just said. Why it takes so long isn't something that can be explained to people that's never done it and for them to believe it. Hell, I'm a programmer and I did art but I've never made a game. And even from what my perspective, it should take a long time.
If you really want to understand, try modding the game. Add a whole new character with their own story and dialogue and all that, like say Mystique, into the game without breaking the game. Someone else already did it so you wouldn't even make all the art assets. It's not like the game is compiled or encoded. You can literally do this with a text editor. See how long it takes you. I'll bet, unless you're cutting corners or not sleeping, it'll take a lot longer than 3 days.
