Even if there is growing fatigue when it comes to superhero movies, there's no doubt that movies from Marvel's Cinematic Universe are the best of the bunch. Heck, some Marvel movies are legitimately great films and even the not so good ones still have great actors playing fantastic characters. Basically, they're all very fun to watch. So why then, do Marvel movies look so blah, drab and just plain bad?
It's the colour grading. There's no pure black value in the Marvel universe and that turns a lot of scenes that should pop, like the epic fight sequence in Captain America: Civil War, into what Patrick (H) Willems calls, "a giant parking lot". And it's true. Looking back at Marvel movies through this video, you'll see how ugly and strangely bland they all are. There are some other reasons why this is (shooting on digital vs film, an Arri Alexa vs a Red Weapon 8K), but it essentially boils down to Marvel's black being more like a very dark grey. Having a darker black value in a shot makes all the other colours stand out more. Without a true black, you get bleh. And that's what we get in Marvel movies.
In the GIF above, the sequence in the bottom right has been colour corrected for a darker black while the sequence in the top left is the original footage seen in theatres.