I get the point you are making but I think its a similar situation to what we had with Lukaku when people slagging him off for what he didn't do....until he left and we couldn't replace him then everyone cried.
Nah. For all of his flaws, Lukaku was an attack unto himself. He propped up some terrible attacking game plans in his time here because you could just lump the ball into the channels or into the box for him and there was a chance he'd make something of it.
Sigurdsson doesn't offer anything like that safety net. If someone else doesn't tee him up with a chance to shoot, cross, or play a through ball, he's not offering much of anything. That's why I disagree when people compare him to Cahill. Yeah, Cahill was a goal-scoring attacking midfielder who didn't provide much on the ball but boiling him down to that conveniently ignores all the scrapping he did to win us the ball in the final third.
If Sigurdsson was winning us the ball high up the pitch on top of the goals and assists, or offering something during build-ups on top of the goals and assists, we'd be a much better side and not even debating this.
We also can't blame one player for shape and team personnel issues.
Sure, you can. The midfield looks entirely different with Davies in the team, giving the other midfielders another option off the ball.