The whole thing is a crapshoot. There's no Bill Jamesian analysis that helps us understand why some managers work at some clubs but not others or predicts which managers will do well in their new jobs, is there? (Of course there isn't.) I'm willing to give Emery the benefit of the doubt, and I hope most Arsenal fans will do likewise. But I don't think I feel any different here than I do when my team makes a first-round pick in the NFL or NBA Drafts: even blind squirrels can sometimes find acorns, and even Belichicks and Ainges can mess things up on occasion. And only time will tell where Gazidis belongs on the Blind Squirrel-to-Belicheck spectrum.
What I will say is that I kinda feel good about Arsenal becoming a more normal club with a normal manager who is actually accountable to the men above him. Of the many Gooners who still wanted Wenger to remain in charge beyond this past season, I wonder how many were subconsciously enamored not so much with Wenger the manager but with a belief in Arsenalian exceptionalism: that it almost didn't matter what results Wenger produced on the pitch, but rather that their club was different and purer and better than all the others in the Premiership. (I'm not sure I'd buy any stock in this theory myself, except for the fact that I've attended enough Premier League matches and been immersed enough in British soccer culture to believe that the proportion of fans who truly hate every other club in the league as much if not more than they love their own club is noticeably higher here than it is in American team sports.) The Wenger model was great as long as it was unique and it worked, but as more managers and clubs adapted to his example and emulated the stuff like his dietary regimens that were originally unique, it worked less and less well. And now the benevolent dictatorship is gone, replaced by a Continental-style, multifaceted hierarchy. Emery may or may not work out. But if he doesn't, I'm confident that he'll be replaced without the agonizing purgatory we experienced for years with Wenger. And if he does succeed, it will likely be in part because of the structure that is now in place to support him. Either way, I'm looking forward to the end of the exceptionalism: Arsenal is finally once again a club more than an idea, and a meritocracy more than a fading legacy.