People forget that even Marvel has had to can a few things. RDJ's cameo in The Incredible Hulk may as well not have happened for all the impact it had and they lost Norton before Avengers. They've also met with challenges of multiple hands on each property. For example, Thor didn't seem to interest Whedon so he gets shafted in the Avengers. AoU, despite not being a particularly great movie in my eyes, is fascinating to watch due to how it fits in the shared universe.
Marvel is not infallible but they are more aware of what makes crossover's work. Seeing Batfleck fight Supes isn't nearly as awesome as seeing IM vs Thor because we can't appreciate how different they are. They were both "made" by the same director in their first/second movies lol. Imagine if Freddy vs Jason was the second Friday the 13th film and a "pilot" for NoES. I mean who cares?
Marvel has only been successful because it has been patient and even if every single movie from here on out bombed(which I doubt) that patience has changed the landscape of cinema for a time. Which is endlessly impressive.