"It was a huge deal for me, very important, to do something that we had never done, in the MCU, and take a trip inside and see what makes these guys tick and what makes them – well, fail to tick".
And he adds: "You know, in every case it really has to do with fear of impotence and isolation and helplessness. These are very lonely people".
And Joss Whedon goes into detail: "That's the thing they all share on one level or another. I mean, Tony Stark could do anything, and he built himself a suit of armour. Thor's on the wrong planet, Cap's in the wrong decade, Natasha was designed never to get close to anyone and Bruce has a problem".
Plus, "Hawkeye has a dark secret that makes him removed from the rest of the group. Finding out what that is is the fulcrum of the movie. It says “Here's the thing about humanity. You have to be a part of it, you can't just save other people".
Joss Whedon style "“ always newer than before

Director's take on the characters was, of course, complemented by certain style tricks. Hear the man speak:
