Fallout 4 was commercially and critically a success. Yes you get people who don't rate it the same way you do for any huge game - look at the commentary around games like TLOU2.
Fallout 76 clearly had a terrible start. But it was a live service game which are often (almost always) plagued with these issues and was rushed out. The game has clearly turned around though, and is now pretty damn popular.
The key thing is that recognize they can't get away with putting out a buggy experience now that they have Xbox's investment behind them and are a first-party studio, particular in wake of Cyberpunk. With the Halo delay then I think Xbox will get that, and you'd hope the resulting focus of having to develop only for the pc/xs gdk plus the extra qa and technical support that Xbox can give them, that it'll be a quality experience. I was surprised they put a date on it so early - I am guessing that shows some confidence, but with 18 months of road ahead of them there is surely still a lot to do.. maybe it's closer than we think from a content creation and playability perspective, and it's not far off being all about polish.
Or.. maybe they push it back (would be a bit of a disaster).
I expect that it'll still fall short for some people because they are in a really tough position. Fallout and ES developers will have all these expectations on them of what the game should be. There will be people that want Fallout in space, and others that want something different that feels fresh. But, I absolutely expect it to be huge commercially and would be surprised if it wasn't critically acclaimed.