We'll never know what a different manager might have done in the same situation as Emery has been in this season, but it's really hard for me to imagine things would have gone much differently. We've had our season collapse later than usual, but we still had it. The lack of quality in this squad goes far beyond technique, physicality, etc.
I keep saying it, but this particular group of players is finished. A few of them might have had something, sometime, but not anymore. The best they can do is give us everything they've got to win the Europa league. If they do that, and then most of them get flogged, I think we can be reasonably OK with how it's all gone down. If not, then our rebuild will be longer and darker still, and that's whether Emery is head coach or not.