It doesn't really leave much to the imagination. You're still stuck as a 19 year old with a living father and dead mother. Not to mention it shows too much. What if i was such a dick that nobody showed up to my birthday party and if anyone did, they were forced to? What if i had no friends? What if no one liked me? The intro just shows too much, it makes it too restricting.
Not to mention how you can't talk down the Overseer or the guards he sends to kill you. You are either forced to run or kill them, no diplomacy allowed.
You do know this is stupid? Sacrificing yourself makes no sense when you have a Super Mutant and a Ghoul that can do it with no downsides. Why would you sacrifice yourself when there's a no downsides option? Sacrifice should be a LAST resort, not something your character just does it because so. If they wanted a noble sacrifice, then don't allow any companion to join you that can do it for free.
This doesn't really work when you go to the wasteland with no weapons or people to protect yourself. He should be dead 15 minutes into entering the wasteland with no protection.
So much of the story of Fallout 3 is done with contrivances and nonsense. Just illogical things happen when they wouldn't if logic was a thing in the game. Much of the Fallout 3 story could have worked if they just rewrote a lot of stuff to make sense but they didn't.
Moira Brown is a terrible character (it's made worse when she instant Ghoulifies and retains her sanity) along with Fawkes. Specially Fawkes, the conveniently sane Super Mutant. No, no, a lot of people that were injected with FEV were turned into mindless ogres but Fawkes is special somehow. Same with Uncle Leo. You can't fill the games with mindless Super Mutants and then suddenly have these two keep their sanity when they turn, with no explanation given.