There are, I think, at heart two primary halves to the problem.
First is how comics quietly endorse Great Man Theory. There's lots of writers in the comics industry that lean left or right as far as politics go, but a fairly common theme is how The Man holds one down. No surprise; a lot of people in the comics industry are freewheeling artsy types to begin with, and lots of capeshit is aimed at kids, teens, and young adults who identify with stories where the hero bucks authority. Hence, authority is dicks, or just incompetent, and the hero needs to find ways to overcome or work around authority to Get The Job Done. It's adversity on the cheap.
The second half of the source is the God of Status Quo. Realistically, a world with Tony Stark, Reed Richards, Bruce Banner, Hank Pym (and so on) would rapidly cease to resemble our own as technological advances proliferated rapidly, accelerated further by contact with alien species and whatnot. Except comics are a medium that needs to remain accessible to the grab-off-the-shelf crowd, so the worlds of DC and Marvel are expected to remain a fair resemblance to the real world. So we get continual handwaves, excuses, memory wipes, resets, reboots, etc as the reason Earth doesn't suddenly accelerate into becoming the capitol of a local interstellar community.