You're assuming modern writers particularly expect their work to stick.

This is work-for-hire with long-ongoing intellectual properties. Someone comes on, they do what they want as much as they can, and they leave when they have and/or want to - with their work in trade, the occasional royalty check in the future, and some parenthetical credits for the next time they get mentioned in a press release.

There's no reason they should have any consideration for the character's place in the shared universe/overall myth beyond what they already have. Any standard like that is the same arbitrary " this is how I think things should work ", just enshrined as general belief.

Given a choice between that kind of standard, typically upheld by fandom, and their own, it's honestly better that they pursue the latter - sure, it's just as likely to reiterate clichés for the concept they're working on, but there's usually something new and interesting in there that there isn't in the former's tendencies to satisfy its proponents only in terms of things that they already know.