Remember some of the first tidbits of info we got on the game was that the roster was huge (informally stated though, I will note) and that they won't release it until it's right.
IMO the reaction to the roster inclusions is pretty blown out of proportion. Disappointing? Yeah. Terrible/pre-order canceling bad/you have disgraced my family bad? No way that all of a sudden the gameplay doesn't look as fun to me or those characters don't look like they could add something. And the product being "right" is probably inclusive of an MCU roster that most modern Marvel fans are into. I don't know how many non-enthusiasts are in tears right now because Ant-Man is in and MODOK is not. I don't even know how much of an intentional bastion of obscure Marvel characters MvC ever really was when the quirkiest picks were because Japan had no idea what characters people liked or not at the time.
Also inclusive, is probably the feature set. They can't get away with releasing an MvC3-esque title again, and if there's been anything at the forefront of their messaging and marketing, it's been the story mode. We saw this iteration in the franchise get a different name and heard the different direction it's taking, now it's just coming into focus - assuming they've got a lot left to reveal in terms of modes, of course. And it has to be exceptional; like SFxTK or Injustice 2 amounts of content.