I have personally never called for Emery's head. I like Emery, as a man, ostensibly, and a manager. I would give him more time regardless of whether we finish top 4. He clearly prepares the players well for the big games, we don't look listless. We have been unlucky and defensively weak. I won't for a moment think Solskjaer got the better of Emery tactically, a refrain used far too often for Wenger's teams in similar matches which we would dominate but ultimately lose because of inefficiency in front of goal and a poor defense.
Consistentcy of results against other opposition is linked with quality and that's where Wenger left Emery short, not the residual effect of his methods, which in my opinion are dissected randomly.
Emery needs more quality and we need to recognise that he has his weaknesses too rather than put them on a manager gone. Ozil was pampered apparently so Emery doesn't actually have a problem with stars, we have been poor defensively under Wenger so Emery's problems are because of him too.
You are right in that there is no one factor but that's not what Anzac was saying or has been saying everywhere.