Oh this is gonna be a long one... feel free to jump to the last 2 paragraphs if you want a tl;dr and my own personal option, otherwise I'm going to be completely unbiased and just give you a general account of what I've observed since the game was announced.
As it has already been mentioned there are 5 major / main Fallout titles before this one. All of these were full-fledged RPGs with a branching story where your actions and choices affected the outcome and you could end up with different or varying endings at the very least.
Now, back to Fallout 76... The game was announced at E3 2018, but everyone already knew about it because Kotaku's Jason Schreier had leaked info about it (as he had done with Fallout 4, and that got Kotaku blacklisted by Bethesda). The leaked info claimed it was a fully online multiplayer game, using the Creation Engine, etc... fans didn't want to believe it and a lot of them resorted to petty insults and trying to discredit the guy.
Given that he hadn't failed at leaking info about Fallout 4, there wasn't really any reason to doubt him now... and it turned out that he was right. Come E3 2018, we are given a trailer that didn't straight up say it, but kind of implied that it wasn't a singleplayer game. Then, Todd Howard, director of the game as well as the go-to figure (along with Pete Hines) for anything involving announcements from Bethesda Game Studios, announced that the game would be coming this year (as it did), that it ran on a multiplayer version of the Creation Engine (a badly aging in-house engine that they insist on using), etc... Meanwhile people were expecting a big reveal about their upcoming singleplayer RPG title: Starfield. And while we got a small teaser, there was no indication of how long it will be until it releases, we also got a teaser for The Elder Scrolls VI, which is only in pre-production and still a good 6+ years away from seeing a release. Both of these teasers were pretty much just a cop out to what was a pretty underwhelming conference in general.
So we were left with the upcoming RPG title being multiplayer, we can live with that right? I mean, even if I have to deal with other people I'll still be fine as long as there are individual instances (like most MMOs with branching paths do nowadays), and I can still play the story and make my own choices. But as it turns out, the information regarding that shortly after E3 wasn't the best. We learned that:
This wasn't the Fallout that people are used to, so a lot of people were already apprehensive... and that's when games media comes in. I saw a lot of headlines about the game with titles that were out of context phrases, or using the journalist's personal interpretation of what they had read/heard. Things such as: