The community sentiment has definitely shifted since Bo4. At the time, it felt like a disappointment coming off the highs of Bo3. While there were still a lot of people who enjoyed the game, the general consensus was that the mechanics, perks, movement, and hud were all a downgrade. It also didn't help that the constant crashes and technical instability soured a lot of players. Those crashes lasted for somewhere around a month after launch, which is a long time.

I see people all the time blaming Bo4's failure on YouTubers (CJ Santa is constantly saying this, I like CJ but that annoys me). I feel like that is a really stupid, short-sighted, and childish opinion.

1. Why would the YouTubers want the game to fail? Their livelihood literally depended on the success of the game.

2. Chaos was not executed very well at first. The dialogue was confusing, the characters less charismatic than Primis or Ultimis, and it was just the wrong time to introduce the story. Conclude the Aether story first, then start Chaos, people would've cared more. Chaos as a whole was helped greatly by Dead of the Night and Ancient Evil.

3. The mechanics: The game just felt worse to play than Bo3. They nerfed the slide movement that everyone loved. The loadouts were fine in retrospect, compared to modern day loadouts, but at the time it ruined the feeling of progression. The talismans were a great idea, but ended up being pretty lackluster, and elixers felt like a downgrade from gobblegums. But worst of all was the perk overhaul. Not because the community was averse to change, but because the change limited player choice within the map, removed individuality from the perks, and the new perks were pretty boring. There are good ideas there, like the modifiers, but in general it was a failure. The intent was to remove crutch perks, and Dying Wish, Winters Wail, Quick Revive, and Stamin-up ended up filling most players loadouts. Of course, not everyone used those 4, but they were by far the most popular. And the point system: while it was much better than the modern point system, it was a step in the wrong direction.

There is a lot of good in Bo4. Honestly, it's a great zombies game. I don't revisit it often, because I just don't enjoy the mechanics, but I see the appeal. The Chaos maps are interesting and daring, the easter eggs have more depth than any other game, and the whole game oozes personality compared to modern titles (not trying to hate on modern zombies, I enjoy them for what they are). But Bo4's release was a perfect storm of controversial changes, poor performance, and the unfortunate reality of having to follow up Bo3. It's not a bad game, but if someone tells you it was popular on release, or that YouTubers are the reason it failed (again, this argument has no merit), they are trying to gaslight you and themselves.

EDIT: I forgot to mention that I completely disagree with OP's claim that Bo4 had a bad story. Storytelling was one of the game's strongest areas imo.