The Captain America movies not being light-hearted affairs like the Thor and Ant-Man movies (and Iron Man 2 / 3) are why they're the best of the MCU crop.
Is Iron Man 2 really "light-hearted"?
No, but the first twenty minutes of it or so could qualify as the cockiest and most-rushed-into-production-and-release music video ever vomited onto (digital) film.