True, but winter soldier itself was a contrived scenario.
Spoilering because some people have yet to see the movie.
from the very beginning, we see Cap taking out a boat full of terrorists damn near single handedly, and the rest of the team is almost redundant. Cap is doing the heavy lifting, while Fury uses Widow to steal the information on HYDRA he's really after...because Widow is willing to do things cap is not, putting the acquisition of the data before the lives of the captives.
Later on in the film we see Captain America and Falcon making a run to take out three rogue helicarriers nearly single handedly. One is a super soldier, the other can fly. Widow is completely useless at knocking out helicarriers, but serves a useful role anyway, infiltrating SHIELD, clearing the way for fury, and releasing the data on HYDRA that dismantles the organization.
It's not that much of a stretch in A2 to see helicarriers replaced with Ultron, and Cap and Falcon replaced with Thor or Hulk. It's all in the writing, and the comics have handled this well for decades.
Winter Soldier is more of a spy film though with organizations of regular human beings. Black Widow worked really well in that setting because she still could feasibly serve in an action role. When even the grunts are out of your power range, that limits the amount of possible roles.