Marvel Studios is a movie-making genius. The studio has jumpstarted an entire genre of films not simply through its shared universal model, but also by purposefully and deftly playing with genre. In giving each of their standalone hero flicks its own genre flavor, Marvel has taken the superhero movie and launched it to new heights.
This is a great strategy, but it is also why the MCU runs into problems when it comes to its team-up ensemble films. While many cite the sheer number of characters in movies like The Avengers, The Avengers: Age of Ultron, and Captain America: Civil War for the over-crowded feeling of the flicks, I think the issue lies elsewhere: too many genres.