Let me preface this by saying that I love analyzing the Fallout games, especially the ones I love the most, Fallout and Fallout: New Vegas. I also really enjoy looking at what BGS did poorly with Fallout 3 and 4.
I'd be somewhat partial to starting up a short, debate-chain here, where someone brings up a topic and I argue the points for or against it, either as a fan or as a want-to-be game designer. For instance:
For the purposes of this thread, I could argue both points if someone brings up a topic/issue, either as a fan or "game designer," or someone could bring up a topic/issue and argue one side, to which I would then agree or disagree and state my points from my perspective. I've seen an extensive amount of content critiquing the Fallout games and analyzing them, but I'm certain there are still a million things untouched by all of those videos and reviews. The goal is to bring them up here, and shine light on new topics.
Look at that from the other side too - when you leave vault in Fallout 4, you can go everywhere, but is it enough itself? There is no danger, no background info, so the game can feel bland a bit, only at some spots without any background reason is a spawn point of dangerous mobs and there are places overun with mobs where you cannot do anyhting else, any other gameplay, but shoot all of it over and over. In Skyrim when you left that cave you had dragons behind you, you had some mission, but in Fallout 4 everything felt so safe or just annoying. And that doesn't have gameplay variability - like a problem and how to solve it kind of choices.
But to make variability I think you have to make some walls - and dangerour areas can be such psychological wall.
Also in FNV when you feel danger, you can also feel immersion. It doesn't encourage exploration, but the game wasn't really exploration kind of game - it was more about choices and multiple playthrough. So there is no reason to go to dangerous areas, because in reality you wouldn't go there too, but it is there ready for choices made and then you can go there - it feels similar to Morrowind.
And I know a player who went north from Goodspring and he had a good fun trying to sneak past dangerous territory, just to get right to the city and it was great that it was possible. I don't know if you could do quests there, but he got his the best guns there and returned to Goodspring.
So yes, it was a bit linear, but because there was logic behind it, it can add something to the gameplay, while some open world (the latest Bethesda openworld) can feel bland sometimes, without point and reason to go anywhere, because the world doeesn't have inner logic.
And because FNV wasn't really open world, it was more like story road to New Vegas with a few stop in between, so it is hard to criticize the game for something which is the main layout, but it felt for me like they got the maximum out of it. And in that linear way with choices it was more similar to the old Fallout games.
But I know players who had fun with FNV who arn't RPG players, who don't care about choices and who like to shoot mobs over and over, so I don't know what they liked about FNV.
And I don't even know if it would be possible if this would be part of Bethesda open world, but for sure players would like to have somehting similar to it - like Morrowind.