Well the fact is that the "infinity war" dlc isnt infinity war, nether the movie or the comic event. Its infact based on the "infinity" event where thanos and the black order go to earth to find and kill his son, thane, whos a inhuman.
Its weird that they named it infinity war as it feels like false advertising but it is what it is. So stuff like blonde black widow was from the movie and its why it isnt included. Infinity introduced the black order to the comics so i assume thats why its mainly them. And why you play as black bolt and madusa because they were the closest thing to main characters "infinity" had. And the reason why hulk buster and teen groot was in it was ether because they were told that they were gunna be in the film or they saw it in the trailer
Hope that helps