Of course there's no curse but that's a bit of an overly simplistic reading.
We've been let down not just by bad managers but bad sporting directors, scouts, agents, players (ahem, Grealish), CEOs.
Yeah we've had a rake of bad managers but the rot in the club goes from top to bottom in a lot of periods, which virtually guarantees bad management anyway.
Emery won't be any more successful unless the poor processes, decision-making, spending etc are fixed behind the scenes.