As has been said pretty much since the start of the replies, immersion does not necessarily equate to realism. It's about consistency (or a distinct lack of therein) within the game world. Hence why you see people complaining about Stimpaks healing Nick Valentine, loading screens when entering houses (and how NPCs simply vanish when transitioning between cells) and even really trivial stuff like how a gun looks or something.
I'm well aware I'm playing a video game, I rarely, if ever, get that immersed into them, and unless something is completely jarring in it's place in the game world, I won't find it anything to "break my immersions". Couple that with just how wack Fallout is, and I doubt I could find much, if anything at all, that would break my immersion, seeing as I have a hard time immersing myself in the world as it is. The Elder Scrolls is way more immersive and provides a far more coherent world to exist in.
Anyway, point being, immersion is subjective, and for people who are genuinely immersed in the Fallout universe (I love the games, but I find it impossible to take the world seriously) even the most irrelevant oversight in design can break their immersion, and consequently, negatively impact their enjoyment of the game.
Personally, I'm more for either good fantasy (Elves, Wizards and stuff) or cyberpunk. This retro-futuristic 1950s America crap is not something I can relate to, in any way. The best storytelling though, is when it focuses on character development and using that as a mechanism for world building. Everything in Fallout is just you (blank slate) seeing everything for the first time or having other characters transpose their perceptions/opinions upon you. I empathise most with my Sole Survivor as a person from the past, seeking answers and revenge, whilst remaining wistful of times gone by. That's about as far as I can connect to Fallout 4.