Yes, the people from Superman's planet (not even named until the end of Year One) had reached the pinnacle of "human" perfection. The art showed them performing superhuman feats on their home planet, I believe.
Plus we have the gods of various mythologies. We have demi-gods like Heracles. We have Gilgamesh, etc.
The idea of people with human abilities taken to superhuman proportions (strength, durability, speed, leaping and even intelligence) hardly began in the 1930s. The idea of people wearing costumes and going by code names (The Shadow, Zorro), and having secret identities hardly began in the 1930s. For some people to single out Superman as somehow 95% original while everyone else was a "ripoff" is senseless if they claim everything he borrowed somehow doesn't count as the same.
The one thing that really generates this claim that Superman was anything but one of the boys in a long line is that he debuted in a relatively new medium called comic books. I love the character but if we just described Zorro or the Shadow or the Lone Ranger without getting into the medium, it would be a rather hard argument that Superman includes anything not already covered.
I once argued that Zorro is a man who puts on a mask and a cape, goes by a heroic code name to disguise his true identity and fights for the poor and oppressed against a corrupt government and other criminals. Someone seriously retorted that he wasn't from another planet and didn't have powers. At that point, the person is just making his argument so Superman-centric that nobody but Superman could meet the criteria. I mean, yes, Zorro's real name wasn't Kal-El or Clark Kent.
But I agree with you. Superman is not a ripoff of Zorro or John Carter or Heracles. I'm just saying that, if someone seriously wants to go similarity by similarity between Superman and Captain Marvel, we can do the same with Superman and a host of characters who were before him.