It is, and here's why, I think: audiences RUIN Marvel films. They're set up to uproariously laugh at EVERYTHING, tuned like mousetraps. It robs whole scenes of drama when light comic relief is greeted with a functional laugh track. When you add it all up, I walk away feeling like I just digested a creampuff comedy rather than a really well-structured, acted, and written film.
Leads into your question @SaysWho? - I still find the Thor/GOTG movies too silly, hokey, and Ragnarok in particular is a 100% comedy which, while interesting in the pantheon, feels rather like Jedi Rocks to me. Too out of place, too cute, too insistent on doing something different for no real reason.
And the ones with obvious weaknesses (Iron Man 2's writers' orgy, for instance) are still problematic. But the mainline Avengers films, all three Cap films, Black Panther, Iron Man, Iron Man 3, and Spider-Man all just nail the comics, care about the world and the characters, and feel less like the candy they do when accompanied by an audience, and more like high achievement in pop art.