Bethesda can't do it. They aren't capable of a decent storyline. Their games are frankly beautifully done mostly empty boxes for people to create their own stories and mods in.
Hell, the Skyrim map is just masterfully done. If you follow the roads it seems big and expansive, and the cliffs/mountains exist to force the player to move around them. But there are lots of little paths and ways to shorten distances.
But a narrative driven experience like fo1 and 2? They don't have the skill.
They screwed up before with automated map generation, and admitted as much.
For Oblivion, they admitted that the Aelyid ruins were mostly computer generated, as well as a lot of the map. Which is why the ruins in particular were so forgettable.
Cyrodil and The Shivering Isles were a blast though. Even playing BG3, with how amazing and stupendously huge it is, I didn't feel that same sense of open scale wandering about (which is why I find their approach in SF so baffling)