It's because, I think, that this scene works naturally. Scarlet Witch had been free before the fight (Like Captain Marvel was), and she specifically jumped in to save Black Widow and the Black Chick from one of those rolling things. So the movie established that all three women are in the same area, and there is a lull because a major war engine was just brought down by Witch. Then Witch gets knocked out, and Widow/Black chick help, and this is believable because where they are was all established--we knew why those three were free to engage, it all was logical.
Compare that to endgame. In Endgame the the establishing sequence before Marvel flies down has every woman specifically doing something, often working directly with their male counter-parts. Now, it might be believable for one or two of the women to get away from their fights--because battles are chaotic. But the fact that half a dozen characters, which were established to be essential to the battle in previous shots, ALL got away from the fights and just 'showed up' right where they were needed....AFTER establishing that the characters were so pinned down only one person could run the gauntlet? Well, that doesn't seem consistent at all. Feels more like they were able to pause the battle so they could strike a pose.
It was just pure laziness, really. It felt awkward because it genuinely looked like a scene some idiot in marketing demanded and the Russos had not established AT ALL, so it was really out of place because the establishing scenes before it showed the characters were all busy/essential where they were. But in Infinity war, the scene felt great because, as said, everything makes sense because every scene leading up to that establishes the logic of why the characters are there'.
