So I'm wondering if all the people claiming it's garbage are people who loved the game.
Basically, the game fandom's opposition boils down to two (and a half) issues:
1) This isn't an adaptation, this is in-universe. Unlike The Last of Us, where they decided "Hey, let's film the videogame cut scenes with real people!" but the show has no bearing on the videogames themselves, Fallout is canonical - this is effectively Fallout 5. So
if the showrunners decide "Capitalists blew up the world because they thought losing 100% of their market and 99% of their investments is a smart move (and also anyone that isn't a Communist is a wrong-thinking monster)", then that's the official backstory for all games in the past and going forward.
2) But they've also said all (and no) game choices are canonical. Fallout has always been a
post-apocalyptic role playing game, namely your choices in the game decide
which version of civilization will rise from the ashes. The show has decided it won't invalidate anyone's choices in those games in declaring "The 75% of you that didn't choose side X were wrong"... by invalidating 100% of the players' choices by saying "Actually, whatever you picked, it doesn't matter, everything blew up regardless of your choices. All of your actions were meaningless."
2.5) Fallout's been made by two distinct groups of people: Interplay (later Obsidian) who made the West Coast based Fallout 1, 2, and later New Vegas, and Bethesda, who bought the rights and made the East Coast based Fallout 3 and 4. Virtually everything in this Bethesda-branded show so far has involved material not made by Bethesda - and everything blown up also isn't Bethesda's material.