To try to answer, succinctly (which I’m bad at): looking backward is easier than looking forward. What I mean by that is since you didn’t get into the series until 3, it makes sense that you wouldn’t have a problem with 3 and 4, since it’s harder to see what the series could have been…as pretentious as that sounds.
Where much of the hate comes from (and I think a lot of it is overblown - I’m not trying to justify the behavior of the maniacs out there) is that the overarching progression of the series feels reset. Fallout 1 -> Fallout 2 showed a progression in a *post-*post-apocalyptic world, with society advancing again, to some degree. Shady Sands grew between 1 and 2, and was the foundation of the NCR.
So Fallout 3 at the time was IMHO a disappointment because the setting felt more generic, and like they were just playing the greatest hits from 1 and 2. I get the arguments that the setting in-universe was hit harder, but it still felt weird that it was post-apocalpytic instead of post-post-apocalyptic.
One reason (as always, IMHO) that New Vegas was so popular is that it continued to build on 1 and 2. We saw the NCR had continued to grow, other factions rise in importance, and generally felt less like the bombs had dropped the year prior. It’s what a lot of folks hoped Fallout 3 would be, in that sense. That’s my own biased view though, so take it with a grain of salt - there’s folks who want more humor, only isometric, more complex and branching storylines, etc.
You’re both in luck! Someone else linked to an article that breaks down how it could work in reality: https://startrek.website/comment/9430643