Hutton allowed 5 goals the other night after Allen was pulled. It's far worse than just a goaltending issue.
That's definitely true, but Hutton has still outplayed Allen to an extreme degree.
As for other issues, it might be Yeo, but these issues were there before. The team gradually slid as the year went on and looked like a mess in January and February leading to Hitchcock's firing. Then, for a while, Allen saved the team's ass while they continued to look sloppy. Only after Allen went supernova did the rest of the team wake up. I suspect Yeo's insistence on playing Allen is that he thinks or hopes the team's mental/emotional issues are tied to or at least will be remedied if Allen does that again.
I also worry that's exacerbating the problem. I'm not even talking about sheer results of Allen instead of Hutton, but the team has to sense something like that going on. And while everyone knows your goaltender is very important, I can easily imagine attempts at sorcery via insistence on starting the underperforming goalie could feel like the coach is saying the skaters don't matter enough and he's given up on their ability to perform or motivate themselves independent of Allen.
I
also worry it's somehow true that the team is broken unless their goalie plays out of his mind for an extended period of time. That they've gotten so entrenched in the belief that they can't score and can't convert on the powerplay that the only options are a one-goal-win or a loss, so they get too demoralized when a puck goes in their net whether it's the goalie's fault or not. And instead of making them do essential things like driving the net or playing stout, desperate defense, it makes them nervous and ineffective.