Marvel Ultimate Alliance 3 had some lingering issues at launch, most notably a lack of key cast members (the same fate that fell upon Marvel vs. Capcom Infinite). But Team Ninja had a plan: through both free and paid DLC, that roster would slowly grow into a formidable force.
The only problem? They aren’t giving us anything interesting to do with those characters.
Source: Destructoid Review: Marvel Ultimate Alliance 3: Rise of the Phoenix