I disagree with you here. The board have done OK since Wenger left IMO. After so long under Wenger, I think it made sense to appoint an interim manager to ride out the transition, and Emery's credentials looked OK as regards potential top 4 - either via the Europa League or via steadying the ship in the EPL. And it almost worked. Until April/May and the shambolic Europa League final we were looking set to achieve Emery's brief.
The board have hardly cheapskated it since - and gave Emery excellent signings to kick on. For me it is squarely down to the manager's failings and cowardice that we are in our present clusterfuck.
What we need now is not a 'showpiece' manager. we need someone to unify the club and show some clarity and balls. Arteta or even Freddie would do for me.