But what's not there, unfortunately, is a solid premise of conflict. Half of the appeal of Fallout is the ability to be awful. You can kill innocents, steal stuff, blow up a village, or do any other chaotic act befitting a post-apocalyptic shithole. And then you can leave your house and walk out into the world, all the while knowing that when that random farm pathetically asked for your help against attacking raiders, you just kept on watching those dumb radscorpions walk right into your frag mines.
Haha! Stupid bug! Hah- OH GOD, THERE'S FOUR OF THEM.
Part of the issue longtime fans have with the newer games is their increasing sense of goodness. In Fallout 4 especially, being evil is kinda half-assed. You can nuke Boston, sure, but you also care about your wife and son, whereas in Fallout 3 you can give a giant middle finger to your childhood friend and bully alike. It doesn't hurt that you feel like you're one dialogue option away from being beaten to death at all times in Fallout 3. In the original Fallout, you can even kill kids, cementing yourself forever as evil incarnate.
That moral ambiguity does not a movie make. You need someone to root for. Even the aesthetics of Fallout rely on this, as they are most effective when juxtaposed with sinister and morally complex choices. The backdrop they create is interpreted by the player, who can either uphold those 1950s ideals or send them up in radioactive smoke. Also in Fallout's favor is that you have hours of gaming to come to terms with the fact that you're a shitty person. Any good deed in a Fallout movie would be countered with the logic of "Yeah, that's nice, but 10 minutes ago you killed an entire family and stole the father's pants, sooooo ..."
No pants? This massacre was for nothing, then.
It's not just the gray-area good guy, though. It's that Fallout has always presented the "bad guy" just as loosely. See, in movies, there has to be a defined hero and a defined villain, but Fallout always leaves you with a sense of "Shit, did I make the right choice here? These people I've allied with kind of seem like dicks." Every faction can seem "good" or "bad" from a certain perspective, but in a movie, you need to know within the first 15 minutes who we're fighting against. Defeating the bad guy becomes the main character's most driving motivation. In a game, that works brilliantly, because you can play through it multiple times to see how different alliances pan out. But in a movie, it's a one-shot deal.