Like everything else, this will go in cycles, as will the hip hop naming convention that Robert mentioned earlier - (Although I’m struggling to think of any recent superheroes who don’t have a code name).
I’d even argue the point to Robert that they are still essentially creating code names;
Kendrick Duckworth and Aubrey Graham don’t quite have he same ring to them.
Kanye doesn’t count he’s a pop star and his ego is so large that he’d never dream of using any name than his own. You will see that in this age, as more and more people seek fame over the the artform or just to make a quick buck or two, that aliases will naturally become slightly less common. That’s just the narcissism that’s present on a wider scale in this current generation.
Is there any need for an alias, I dunno. But it’s far more marketable and my son doesn’t point to my Avengers tshirt and exitedly tell me ‘Bruce Banner’ and ‘Steve Rodgers’. It’s Captain America and Hulk and I think that will always be the case with superheroes.
Harry Potter is a school child who can do magic and retains his name to be relatable to other kids.
James T Kirk is the captain of a ship and can’t really go under an alias.
Indiana Jones is an archaeologist etc
To answer the question, I don’t think we’ve entered a post superhero codename world, but we are at saturation point where new superheroes are less and less likely to be created because it because more and more difficult to create new properties.
Even the most successful new character in recent years, Ms Marvel, is just a new take on an existing character, which works as a new entry because the character is so interesting and appealing because she leads such a different life to what many of us are used to (and gives young Muslim readers someone they can finally relate to themselves in terms of family life etc).