"Cancel Ant-Man! The project is hopeless!" The headlines are blaring. Fingers are being pointed at Marvel over how poorly they are apparently treating this project since director Edgar Wright diva'd his way out of production due to "artistic differences".
Marvel has a certain seal of quality and guidlines for their growing movie universe; it would be natural for an in-house script supervisor to make some necessary changes to make it fit into the larger scheme of things. This is most likely the reason why Edgar left the project. The deluge of directors being attached to the project, only to unceremoniously leave, since Wright's departure, is more likely due to the incredibly sudden job offer and the tight timeframe associated with it; also, none of these directors probably know the character like Wright does.
Not to beat a dead horse, but it really is a point in Marvel's favor that the company repeatedly changed its production schedule over the past EIGHT YEARS, allowing Edgar to take his sweet ass time, whether it be stalling the project in favor of Wright's The World's End, or allowing Wright grievance time for the loss of one of his close friends. This is a HUGE priviledge for Wright; when it boils down, Ant-Man is not Edgar Wright's property.
This is what separates the project from something like a major studio buying a completely original script and changing it to the point of unrecognizability. Yet, Wright's mindset was that the project WAS incredibly personal, and Marvel did its best to cultivate that mindset. Remember, the film was originally going to be a Phase 1 project, meaning we could have gotten the character's true characterization as a founder of the Avengers and the creator of Ultron.
Why punish a company who repeatedly accomodated your busy schedule by ruining the development of the movie a year before its release? He had EIGHT YEARS to get this project off the ground, claiming how important it was to him, yet continually blowing it off. This film could have stood out as its own entity and been the first film of the entire Marvel Cinematic Universe like Wright's original vision, yet he missed that train.
In the end, Wright only screwed over Marvel by leaving the project. It'd be like a director being attached to an American RODAN reboot for years only to get pissed at how he needs to fit it into Gareth Edwards' Godzilla timeline.
Wright should have just taken one in his self-important dignity and finished it, despite that fact that some Marvel pencil-pusher inserted an Iron Man reference into act 2 of the film. Who knows, maybe he's just pissy that Marvel cut out the cameo he set aside for Simon Pegg and Nick Frost.