Simply : Welcome in the console world !!
Since i start to play fallout 4, yes i actually play it and finish the main story with the BOS, the institute and the railroad. I think the Fallout series take a big step and become a console game. It simplify as hell, the world is scrip like we never saw before, npc unkillable, really little impact on the world, most of the location hide behind loading screen ...
The game make the player think less more action, less RP and RPG stuff.
Look right at the start you get a power armor, before you had to play hours for have it. With the minutemen really soon you take the castle with a big boss in high level like mission. Everything is made for give fast action and power. That simple i feel like i play a COD.
I think at the end the problem is not the game. the game is ok nothing amazing but not bad. The problem is the target of this game, i can bet that most a people who like this game are young and didn't grow up with the fallout 1 and 2 ( fallout one was the first pc game game i buy). this game is a fast action , fast power, need less thinking and more action.
the original fallout series was a deep rpg, a mature game, where you had to play hours for earn your power, where each of your action impact the world .....
So that explain why is so much people who don't like the game. Is a confrontation between generation. And sadly Bethesda will make game on the way it make money, they don't care about the heart of the game.