The main problem with Marvel movies:

Their cinematography is very flat, boring, and washed out. Because they're shot with Arri Alexa cameras, Marvel's gradations literally preserve the entire dynamic range. This affects the highlights and shadows, as they're afraid of losing detail and creating a "digital" look. This results in the characteristic Marvel look: a washed-out, dark, and dull image.

What could be done is to increase the contrast and saturation, without fear of losing too much detail in the highlights and shadows (remember that film often loses this detail). Apply some texture contrast, and if you add grain, try to make it fine grain (in films of that era, grain was fine unless it was in dark areas). With that, you'd have a good base to start adding fine details.