An "all star" movie of captains and first officers wouldn't be like that at all. It would be too contrived. First, it would be contrived in how they get together from across time. Second, it would be contrived in how the "work" in solving the conflict is divided up (do we want Janeway to do this or Picard; should Sisko lead the ships into battle or Kirk; is someone the "leader" of the captains; should Archer be the ultimate hero or should it be Kirk).
For Hollywood hacks yeah. Whendon did just fine.
Who's Iron Man anyways?