ResurrectedContrarian
Suffers with mild autism
The general philosophy that I've recognized in all of these modern productions is this: All of these people you used to see as the outliers are just like you. And so, when they write these characters, they are written with the typical archetypes overlayed on top of them. They can do all the things you can do! See? They're not so different.
Again contradictions. You might argue, "the point is to show that this trait doesn't define them", and again you are stuck with contradictions, "if this doesn't define them, then why bring it up?". "Because it doesn't define them...".
^ This, in particular, hits the problem really well, thanks.
In Disney (Marvel / etc), the concept of diversity really comes down to what you described, which is the replacement of all definite characters (people with a particular, specific set of attributes that define them, and make them interesting to encounter) with mere placeholders, or costumes, that any of us can fill. They want to say "any one of us can be this badass character!" and so they use diversity (mixing up visible combinations, genders, races in ways contrary to expectations) only in order to make the character seem open to any interpretation, not in order to tell a real story about how that person's specific existence as a woman etc contributes meaningfully to who they are or to how they tackle the world differently from a man.
It's the kind of diversity that corporate pop culture loves, though, because it sells products... it says "any kid can be the Star Wars hero, can hold the lightsaber!" when really, it's better for us all to encounter characters that are different in meaningful ways, not just in order to mimic a college brochure full of carefully PR-crafted "diverse" mixes on every page.
Difference is good, but only if it makes a difference. Using difference only to subvert any expectation of roles or types is just useless and actually reduces the characters.