The Mezzanine

Hmmm.. I just re-watched some of these films and disagree.

Captain America actually is an average Joe, from Brooklyn, who was beaten up a lot as a kid. Had no money. And just wanted to enlist in the War effort. He volunteers for the super solider program and voila, no longer average Joe.

Thor is from another planet where he is a God, sort of similar to Kai-el aka Clark Kent aka Superman. The point of Superman, is Clark Kent is the disguise.
Also Batman is a DC superhero who is super-rich and funds his whole enterprise, while Tony Stark got captured ended up having his heart critically wounded and had to put an electronic device inside it to keep it ticking and armor outside to protect it -- Iron Man sort of comes out of his need to protect his weakened heart. He's basically Batman but with a bit more of a twist and more science involved.

Black Widow isn't wealthy -- she's a Russian spy, who is trying to redeem herself and got conscripted at an early age.

The Hulk was Bruce Banner, a scientist trying to find a cure for disease through gamma ray technology and well -- it back-fired on him.

Ant-Man is a struggling single Dad and had been a thief, but is trying to get out of that. And got selected by the original scientist Dr. Henry Pym.

Captain Marvel is a pilot who dreamed of being a pilot since birth and ended up accidentally getting embued with super strength -- she wasn't rich to start.

I don't think you know these superheros well enough to make a judgement? The MCU like the DC verse and Jossverse is rather multi-faceted.

And I guess you don't think of Wonder Woman, Superman, or Batman as heroes -- because all three are, I hate to break this to you, super-wealthy.