You have no understanding of Captain America.
Like, you're literally completely wrong.
It is genuinely hard to be more wrong.
Iron Man is the symbol of American military might.
Captain America is a champion of what America is MEANT to be, not what it is.
Captain America QUIT being Captain America when America turned against the values it is meant to stand for (liberty, justice, equality, freedom).
Captain America does not work for America. He champions the ideals that it is meant to embody.
He doesn't take kindly to America dishonoring itself, and debasing the noble ideals for which it ostensibly stands.
The Marvel Civil War was a perfect example of this, in which the US Government began infringing on the rights of its superhumans and attempted to force them to register their identities and powers.
Iron Man was the commander of the superpowered forces (both pro-registration heroes and supervillains forced to serve the government) working FOR the government,
while Captain America immediately became the commander of the resistance, even though it meant being hunted by the government, being branded a traitor and criminal, and even having to fight his pro-registration friends.
"On Olympus, we measure wisdom against Athena...speed against Hermes...power against Zeus. But we measure courage...against Captain America." - Hercules
Beyond that, YES, Steve Rogers is a relic of a different era. That's half of the point of his character. He's a man out of time. Lost and isolated from the world he knew and the people he cared for. But while Steve Rogers is an anachronism, the things he stands for as Captain America are timeless. They are things he stands for no matter where he goes and who he deals with.
That's the point.
Captain America is the hero that all other heroes in the Marvel universe look up to.
As a character, he's beyond Superman.