When just about ever single player from the 2021 team declined, some by a ton, I'm thinking the players are mostly to blame.
I realize you can't fire the whole team, so the age old tradition is to blame the manager for not motivating or preparing the team and the GM for not being a fortuneteller.
Sure, on the game threads, we hear this guy sucks and that guy sucks, and "no way should this guy still be on the team," but just about evert single carry-over player has let the team down, including Bogey, JD, Devers, Nate and all the "team leaders."
Of course, Cora and Bloom share in the blame, but Bloom has other priorities besides "win now." To some extent, managers need to look at the whole 162 games not just go all out to win every game, but not to the extreme Cora seems to take it.
On the specifics you mentioned:
Duran was not this bad on D in AAA. I think most GMs give call-ups time to adjust to the pressure and new level. Did he give Duran too long a look? In hindsight, the answer is easy.
On Dalbec, many felt he should have been demoted, last season, but look what happened. Then, this year's flip flop. Many wanted him demoted again, and Cora tried Cordero at a new position to fill the Dalbec benching with what he felt was the best chance to improve our 1B production. Cordero was showing signing of hitting better than almost anyone but our big 3. I'm sure he expected a learning curve on defense, and he got one much worse than any of us wished. Did he stick with him, too long? It looks like it.
I'm not one to say he should have made a late May trade, unless I know for sure, what 1Bman any team was offering, but Bloom did not make a trade, so it's his fault not Dalbec's, not Cordero's, not Arroyo's? I just can't bring myself to see it that way, and it doesn't concern me that I may be in the vast minority among fellow Sox fans. Show me a trade that was offered in late May through June, and I'll throw blame or laugh at it.
On Bloom, I would have moved JD down to 6th and then maybe 7th in the line-up, but some would view that as a slap in the face of a vet. Plus, with so many injuries, it's not like we had much better options.
With Bogey's power sapped, and his BA and OBP still high, I might have tried leading him off, but oh, don't go there! Many posters swear players are creatures of habit and hate being jerked around in the line-up, and we don't want to upset an established vet and team leader.
In many way, a manager is damned if he does and damned if he doesn't. Brining in Ort looked, to me, like a horrible call, and hindsight proves it was. I'm sure he had his reasons, but the end result matters more than anything to most. I never let a call a disagree with here and there bring me to the point of calling for a manager's firing. I try to look at the whole picture (not that you and others are not,) but to me, the whole picture is not just looking at the team record, ranking and total budget. We all see the same things differently, and I'm not saying my view is superior, but I do think JH looks beyond just the fact that we are spending a ton and sucking on the field, currently and choosing to blame Bloom & Cora for most of that.