Because โDO A BARREL ROLL!โ is natural and diegetic ๐ญ๐ญ๐ญ
If you don't know what I mean by "in service of the medium," consider an example that people keep using: Star Fox 64. The dialogue is campy, but everything about it is natural and diegetic. You "believe" it, for lack of a better word. Characters don't speak without reason. It's always for the purpose of worldbuilding, it never actually interrupts the gameplay (save for incredibly brief cutscenes), and none of it ever feels like it "came from" our world. You are inhabiting a frame of reference within a world that's separate from your own, and the game succeeds at selling that to you. Same with Max Payne or System Shock or Legacy of Kain or any other example you'll see people using.
By contrast, "MCU dialogue" fails to sell itself as diegetic even when it's trying to be. You hear a character say something like "uh, did that just happen?" or "focus, M" or "maybe using X will help me do Y" every ~30 seconds and you immediately form a mental picture of the frumpy writer's room women who insisted that you be subjected to that constant quipping and pestering, often by breaking the flow of the game itself. You don't "believe" it at all. It reminds you that you're Consuming A Product that was designed entirely by committee.
In some ways, current-gen games are actually worse about this than Marvel movies are, because games run much longer than movies do, so you are expected to endure this 5x, 10x, 20x longer than a movie would ask of you.
(Of course, all of this presumes that You are a Real Person and not the sort of person who would defend this or fail to notice it in the first place)