While, I hate review bombing and think it's a very dumb tool of a collective of passionate but very misguided idiots (this is fanbase that review bombed Last of Us 2 because they didn't like aspects of the story). I will say, in this case, it's not getting review bombed because the episode lacked action or focused on character development primarily. It's getting review bombed because they significantly deviated and changed the purpose of a great character in the game (Bill). What Bill emphasized in this episode thematically was there was hope for love and happiness in this world. In the game, he emphasized bitterness, and that love and trust will get you killed in this apocalyptic world. And, when you dramatically, change what a character does thematically in a story that has a very passionate fanbase, usually it results in backlash. Just look at what happened when Jack Reacher got played by Tom Cruise or how book readers reacted to certain changes in Game of Thrones. Not saying it's warranted, but I think you are misguided on one of the major reasons this episode is getting backlash.
I love the Last of Us games, and am one of the biggest proponents of HBO's premium shows (The Wire and Sopranos are my two favorite drama's of all time by a wide margin). I generally think video game adaptions are an absolutely terrible idea, but was hopeful for this one given the people and studio behind it. I'm enjoying this show, and hope these changes result in a masterpiece, but I am curious on how this change thematically plays out.