People read way to much into Joss Whedon's sarcastic, self-deprecating humor.
It took me watching a few interviews to get it myself, but people have been taking quotes, then taking them completely out of context to attempt to decipher some hidden meaning behind them ever since AoU came out.
Obviously Joss was overworked and wasn't exactly happy about it, but from reading/hearing his interviews in the press run (including the quotes/articles in the OP), I get the impression that this wasn't Marvel cracking the whip and breaking his spirit, it was his self-imposed burden.
Just look at the quotes.
He's not saying he was an idiot for wanting to make a great movie and then having his hand forced to make something more marketable. Read the context of his quote, he is saying the burden of making the 3rd highest grossing movie of all time meant tons of expectations, not just from Marvel/Disney and his fans but himself. After years of work in TV, suddenly Avengers is what he becomes known for and it heaped him with praise of being a genius that he didn't get to ease into. He's not saying "Look at Avengers. There is failure. There is compromise." as if Marvel was making him do all this stuff. The context of the article is that he didn't get as much time with Avengers as he would have liked and with AoU, he had more time to do what he wanted to do. The compromise and failure is from being known for this huge film that neither he nor Marvel expected to be quiet as big as it became and suddenly that's his legacy as a director, a work that he doesn't feel was even his best, nor what represents what he could do as a director.
I think that's the most obvious impression I get. Joss wanted to top everything from Avengers not because he was mandated by Mickey Mouse but because he felt he could. He
knew he could do better. People said the action scene were weak, he wanted to out do himself, especially as a comic book fan to bring to life the characters and the action in a way that respected the source. People said that Hawkguy was terrible or Hulk and Black Widow didn't get enough development or their own movies, he decides to give them the best treatment he can to make up for it. He chose Ultron as the Avengers villain that he wants to see the most. He already is developing this Tony and Steve personality clash because that is who these characters are, not just because Civil War is up soon. Luckily for fans, it works out perfectly.
Unfortunately, that all means that his desire to make the movie smaller, was outweighed by his desire to make a better film. His ambitions to make a movie "worthy" of being 3rd top grossing film of all time, to try to guess what made it popular, is enough to drive you mad. I've heard musician say it often as well if they have a hit song and they want to replicate their success, it can stifle your creativity by trying to live up to your legacy.
Nolan obviously has more experience as a film director and didn't have the burden of continuity on top of that but I don't believe that Nolan didn't feel the pressure of having to follow up The Dark Knight with The Dark Knight Rises. It suffers from many of the same pitfalls as AoU or just any sequel aiming to top itself.
With Avengers, Whedon may not have even tried as hard to weave all these different character together as people might think. It might have just been what how he would naturally try to write for all these character in an ensemble cast, give everyone a chance to shine and develop what each character would do. Suddenly that movie is a huge hit and expectations skyrocket through the roof and Joss may start to extend beyond his reach in trying to be the very best he could be.
Maybe Marvel did want him to make the movie smaller but due to the way Joss talks about it, the way he says he "lost the movie" and why he seems to believe cutting down the time so much is the best decision, I believe that somewhere along the line he must have started doing things to do it and forgot that developing Black Widow more or developing Quicksilver and Scarlet Witch more, might not service the main story or the film enough and that it has to get cut to stop the pacing of the film feeling too uneven or bogged down. He comes from a TV background but he wants it to be a film and feel like a film, not have the critics rag on his film for being too much like TV. It's why he dreaded people saying they were excited to see what was next because not only does it mean that he failed making it feel unlike TV, in his mind, but he also didn't get rid of all the extemporaneous stuff that didn't support the main film. That's why it feel like they might have taken a machete to the film in the editing room at some points, because Joss wanted to make this huge film he made feel as streamlined has humanly possible.
I mean, think about it, this guy had an even bigger budget than last time, there seemed to be a lot of shots that got cut from just trailer footage and some stuff with effects work that was already done with whole action sequences that didn't make it. This guy could basically make whatever movie he wanted to and it was probably the lack of restrictions that caused him to go over board, rather than Marvel being some slave drivers, that caused him to be so stressed. James Gunn seemed to have been equally heavily involved in the whole process, but it seemed to be his own choice from saying how much he wrote for the outline, design document (which he said he practically came up with a book when they were asking for a few pages) to choosing to be very hands on with the music choice to working with the concept artist directly to working with the 3D conversion of GotG. And if you think about how big this opportunity is for guys like Joss or Gunn, it makes sense they want to give it their all to really put their stamp on these movies. That's why Joss sounds like he's actually proud of what he made:
Im now coming out the other side, realizing that once again, for all its many varied and soon to be heralded flaws, its my movie, he said. Its the movie I set out to make. And I have the honor of saying, its fucking bonkers. So theres that.
That doesn't sound like the sentiment of a man who was forced to make a movie he didn't want to make. A man under a lot of pressure to deliver and on a very hectic, fastracked schedule, sure, but you are not going to be proud to put your name on a studio film that wasn't your own creation, a film that will inevitably be a reference point for your career that everything will be compared to.
