Looking back at all the characters that Marvel Studios brought in the MCU, admittedly, some of them are could’ve become the franchise’s first flop.
After Iron Man, and certainly after Captain America and Thor, and certainly after The Avengers, Marvel Studios could have made, theoretically, a nice game plan only making sequels to those movies.
At this point in time, nearly all of the characters Kevin Feige listed as hopeful risks he’s been able to make.
Despite this, Marvel Studios has been undeterred to introduce all sorts of comic book characters in the franchise regardless of how uncertain they of fans’ reaction.