As far as the story goes it felt to me like a retread of NV: unite or conquer the wasteland through a faction. The decision to have voice acting and a central story felt like a necessary, modern improvement.
As to the simplification of the systems that helps achieve mass appeal so I can understand the developers' decision to do so. "Gamers" from the NES generation are now working with tons of disposable income but not the time to invest in all the AAA-titles available. Furthermore there are so many other distractions game companies need their games to have mass appeal to be considered successes. I find that mods tend to fill in the gap allowing crippling levels of difficulty if you choose to install them
Skyrim got a lot of the same criticisms that Fallout 4 got in being too simplistic. I see a lot of Skyrim in Fallout 4.
I think you hit it on the head though with preconceptions and major franchises. Hard-core fans want more of the same so any changes will be met with criticism. The problem is the hard-core fans will buy it no matter what and developers want new people getting hooked on the franchise.
You're quite right for the most part, but I wouldn't say voice acting or a central story is necessarily... necessary.
Other RPGs -- again, to use Skyrim as an example -- have sold exceptionally well without either of those things being present in any meaningful way. I sincerely do not think Fallout 4 would have sold worse had it lacked a voiced protagonist. The reason Bethesda's RPGs (specifically their RPGs, not their other published titles) have sold so well, in my humble opinion, is their emphasis on complete and total freedom, as well as roleplay.
Your character has no pre-set goals, no real backstory other than "prisoner" or "Vault survivor." Everything else is largely up to the player. However, that's the decision they made, and it's likely future RPGs from them will follow suit. That's what mods are for!
I also don't think there's anything wrong with "hardcore" fans voicing their frustrations with the current state of some of their favorite franchises, so long as it's done in a respectful manner. Personally, while I'm not one of them, I do think there are a lot of elements of the older ES and FO games that could actually work very well for a modern audience, but have simply been forgotten about. Spell creation, for example - a fun side addition that doesn't need to be overly complex, but got lost in the "modernization" of newer ES games.