The fact is FO4 is very mediocre and failed to produce anything meaningful in the long term except herds of low-standard reddit hipsters
The fact is, you are not stating a fact, but posing your opinion like it is one.
You hardly talk about the game at all when you are posting your opinion.
How much of the game did you play? Did you acquire, plan and build settlements? Did you come to their aide when they needed help? Did you grow your settlement? Did upgrade your settlements to get the happiness factor up. Those duties are a part of the game. And once you have to worry about multiple settlements (I have 16), that is going to take some time. Yes you can chose to ignore them but I found the settlement part of the game fantastic.
And IMO, the sim part of this RPG/shooter is meaningful and I want more. When I play SimCity, I turn off the disasters because it's meaningless to me, but in F4, building, populating and defending your settlement has consequences. I've had NPCs die while defending their homes. I hope one of the DLCs Bethesda has planned addresses some of the problems and is settlement oriented.
So for me, No, Fallout 4 did not fail. I got 250 hours into Witcher 3, but I got over 500 in Fallout 4. There is just so much to see and do.
Another thing is are you reading the terminals, books and holo tapes within the game world? People talk about Bethesda not having any writing in their games but there are hundreds of mini-stories that are very compelling within the game world.
There is one story secured by reading the terminals where two twin brothers survive the nuclear holocaust and bunk together, but as time passes they both become more and more crazy and then . . .
Or there is one terminals story where a family has made a bunker but the wife did not make it back in time. The father is trying to send messages out to his wife hoping she will make it to him and the kids, but when you get in the bunker you find . . .
Or there is one building on the docks where the owner has tried to raise and tame Mierlurkers. He believed if you talk to them nice they will behave. While you are exploring this site you can hear this continuous happy talk over the loudspeaker
imploring his little mirkies to be good and not eat meat.
Or there is one building you break into. Two skeletons are laying of top of a safe one grapping the other by the throat, the other with a gun in his hand. Both heads turned toward the window.
Or the home where the little kid skeleton is in a big box playing checkers with his teddy bear friend.
It's like the designers said what would be happening in life, what would be going on, what would people be doing at the moment the bomb went off? Each Fallout game they get better and better at depicting that moment. These little mini stories and scenes are draped all over the landscape and it makes exploring this world so very, very compelling.