7. It's The Producer's Vision Over The Director's
Ever since Disney bought Marvel, one director has been brought on for each film. By the time Age of Ultron comes around, only Joss Whedon will have stayed on for seconds. The chain of shifting directors proves that the producers don't care about their characters being developed fully. As stated before, the characters were all thrown into the mix having only been half-baked, so that no arc could be created for each one individually. This plan is genius for multiple sequels as it allows a superhero to go through many adventures without ever establishing a "concrete ending."
Wasn't Jon Favreau going to be in charge of this entire franchise? Well, that might have been the case had Marvel stayed independent. When Disney flooded the executive offices and gave its producers far stronger control over the whole project, Favreau was reduced to executive producer on The Avengers and didn't even return as director for the dividing Iron Man 3. The reason he gave the public? He wanted to direct a fantasy adaptation of Disney theme park the Magic Kingdom - but you can tell this is a lie because Magic Kingdom hasn't even entered production yet!
Now, you would think that having a consistent team of leaders would actually be beneficial for a large-scale universe of this kind. Truth be told, though...