I am not saying they are.I am saying there is a limit to flexibility and layers have a core.If batman sucks at detective stories and crime drama/thriller stories.Then people won't care who he has a relationship with..The superhero genre is flexible.but,it does break.I mean,thats why we don't have basketball superhero sports book.Where a caped crusaders leaps and throws balls into hoops.(i wonder if they could do that.i mean that would be fun..now that i said it out loud)
you don't need a ship to get inner workings of a character as well.There are platonic relationships,you know.I mean,brother,friends,comrades,father -son,rivals,mother-daughter, team-mates...etc.All sort of dynamics can do that.while romance can be a great Avenue.Certain stories need that crux.For example:-maybe a fantastic four because of the family theme.berserk needs it even though it's a dark medival fantasy story.Because that story requires the love triangle leading to a tragedy.For superman and zorro the love triangle with secret id is more intrinsic.but,these guys don't need it and can without it perfectly fine.batman?even less so..batman doesn't need it.Spiderman might because of the teen drama asoect
But,yeah!I don't think it's a requirement to have a ship for superhero story to be successful.That's all i am saying.Let alone focus on it much.