My problem with the fire Farrell narrative is that, outside of obvious cases like Valentine, the only reason it is even considered is because people care about the Red Sox doing well, and when they are not fans NEED an explanation, it's just an natural emotional response. Especially with sustained poor performance, fans naturally look for patterns, and one of the few common threads between 2014, 2015 and now is Farrell. Obviously he probably has SOME effect on overall performance, but it's hard to say how much. But if you're looking for answers and there's only one name that you can really point a finger at, you're more likely to overestimate his effect on overall performance.
Not too get too meta about it, but once you let that emotional bias permeate your thinking, then every single move by Farrell that doesn't work is now "wrong" because it confirms your bias, and everything he gets right is ignored or dismissed as a no-brainer, blind squirrel, or possibly even still wrong. I'm not saying there aren't legitimate issues with his in-game strategy, I'm just saying that having this bias makes a fan actively use hindsight and logical fallacy to attribute blame to the manager. My pet peeve is when fans "can't even imagine what Farrell was thinking" with bullpen usage, or Xander's recent day-off calamity, when it takes a pretty small amount of consideration to see that there are multiple options, all with pros and cons. Simply by making any decision, Farrell is in the wrong in their eyes because he wasn't able to miraculously capitalize on the upside of every single option while avoiding every single downside. Because Farrell himself made decision A, its obvious to fans that B was the better option. Then you can snowball and echo chamber effects, and it all piles up to be really biased, vile, and offputting discussion.
Fans never have to have a clear policy, or a clear value system that they stick by in these situations, and they never have to explain themselves when they deviate from that policy, even if they have one. No one's ever going to hold them accountable to their opinion on when Xander should have sat in this series, and ensure they stick to it the next time a similar situation arises. The only policy fans need to have is "win now, win more", and that covers everything: bunting, days off, batting order, bullpen usage, long term player development, the works.
Farrell is in a particularly difficult spot, because he's finished last two years in a row, whether he was a major factor in those outcomes or not. Managers get fired for that type of underperformance all the time, it certainly wouldn't be unprecedented...