Respecting canon has no consideration in art? Can't say I agree. If I make a movie where the character and story are an allegory for the story of Jesus, the canon story of Jesus as depicted in the King James Bible is going to have ramifications for my own and if I wildly deviate from that then I don't think the movie would work.
Obviously the Batman canon hardly compares to the Bible but the point is working within canon absolutely has a place within serious art.
I like the first two Raimi Spiderman films and Spiderman Homecoming was cool. That said I see where you're coming from.
I think people misdiagnose the problem with Superman. People will often say something like the problem with him is that he's too overpowered. But that's why his main nemesis is Lex Luthor, a powerful businessman integrated into mainstream society who he can't confront with brute force. And sure he's an alien but the whole point of the character is that even an (illegal?)alien from a different galaxy can become not just an American but a great American and an embodiment of all that's good in America.
I've said this elsewhere but I think the problem with Superman is that he has the ethos of a New Deal Democrat with a middle America flavor and people on both the left and right find that alien(pun intended). Right wingers prefer heroes like Batman and the Punisher and leftists prefer more urban, diverse heroes that you tend to find in the Marvel canon. If someone could really write an authentic Superman I think it has the potential to realty resonate with Americans but its an uphill battle
Iron Man probably has the most mass appeal because he embodies a lot of(I would say largely negative and distasteful) trends and notions in modern society; his abilities play to notions of scientism, his lifestyle to our admiration of wealth and hedonism, and his personality to our absolute allergy to sincerity and our preference for ironic detachment and snark. I really hate RDJ's Iron Man even though I give the actor massive credit for his performance as the character.
Bruce Wayne is also a playboy but in the Nolan trilogy the playboy dimension is more of an act, something Wayne plays up as a cover. RDJ's Iron Man is an unironic playboy which to me is really off putting.