Is Joss Whedon to blame for sitcom tone of all new MCU product?
I remember Iron Man having humorous elements, but that was mostly because Robert Downey Jr. brings that persona in most of his projects. I don't think their Thor or Ed Norton Hulk was very funny, from what I remember. Captain America: The First Avenger had more of a nostalgic feel about it, and it isn't what I would call "fast-paced."
Honestly, I don't think until the Avengers came out, did every Marvel movie have to be this nightmare of endless self-referencing and one-liner after one-liner after one-liner. Guardians of the Galaxy sort of perfected this irreverent tone, and was hugely successful. Now, every Marvel movie is virtually a sitcom with superheroes.
It's entertaining and has obviously worked well for Marvel and Disney, but it really is the definition of disposable. No way they will ever abandon this recipe unless box office receipts begin to dwindle.