Yes, we're operating under assumptions on any side of this argument. But I'm basing my
speculation about what drove the wedge between Wright and Marvel on
rumors from El Mayimbe. Granted, "Eh Maybe" is a highly unreliable hit-or-miss source, but I'll give him brownie points for correctly awarding the Daredevil casting call to the obscure choice of Charlie Cox just within the past 24 hours. That being said, Mayimbe was very specific in what caused Wright to divorce Marvel:
So, according to LR's source, Feige and Company (i.e., "the big four at Marvel") specifically told Wright to change the morality of the story to be palatable to Disney (read into that what you will --- my own guess is that it was simply about language, violence and adult themes, all items that have generally pushed Wright films into an R rating before) and to specifically include franchise characters; i.e., Avengers.
So maybe Eh Maybe's wright

oldrazz

and maybe Eh Maybe's wrong, but his source definitely seems to echo the narrative of the development (or lack thereof) of this project since 2006. In the end, the sticking point was the same it's always been: Edgar Wright wanted to take Avengers out of the Avenger Universe to make a standalone movie, and that flew directly in the face of everything Marvel Studios is trying to do in creating this shared multiverse.