It’s parsimonious to suggest that given how complicated superhero comics continuities can get, current non-comics adaptations often end up being less faithful for whatever reason, preferential or practical. Unsurprisingly, certain details are left out for good for being too unimportant. At least that’s how it was like.
Increasingly producers are compelled to pander to hardcore fans even when they’re also compelled to adapt the same stories and characters for wider audiences. For most of the part they managed to compromise this real well in the form of references. Not that they’re wrong but they often pander to those who are in the know.
If you reference music a lot, a la JJBA, you’re going to attract music nerds. That’s predictable. Lots of people listen to music anyways. Superhero comics are another matter, not too many people read comics let alone on a daily basis. Even with pirated copies around, not too many people have the time to read comics.
Far fewer people read superhero comics so it seems the audiences for superhero productions and superhero comics can be disproportionate. If Ranker’s assessments on the differences between Batman movie and comics fans are any indication, despite an overlap, one would expect MCUverse fans to be younger and more invested in other filmed productions on average than they are with comics.
They’re bigger than the differences between JJBA anime and comics readers (or for another matter, Harry Potter film and book readers) because for them filmed productions practically act as adverts for the stories they’re adapted from and do a good job at introducing them to the source materials.
The MCUverse does this to a lesser extent (and the same can be said of DCAU and Teen Titans) because the source material’s really complicated. I’ve spent more time hanging out at written profiles of every DC character than reading the comics they’re in. Seriously, it can be that hard to track their appearances in every title within a shared universe.
If you find Jean Polnareff in Chinese cartoons, he’ll always be a Jojo character. Much of it is extrapolation and personal anecdote but it still makes practical sense on why JJBA fans can relatively easily get into the comics version but not so much for superhero fans whose first exposure was the watered down telly or film versions.
So they wound up relying on easy to understand profiles instead. That still rings true when you think about it though I could be wrong about it.