I'm sorry, but there is no solid "representation" argument to make. Either you care about being true to source material, or you don't. If a character isn't black, or Asian, or Latino, or any other "non-white" thing, then they shouldn't be cast as such. Period. It isn't "a new take on an old favorite", it's lazy, pandering casting practices.
If they want more "representation", then make new properties or characters who are those things. Aquaman is a white-looking blonde, blue eyed man. That's how he should be cast. Iris (and Wally) West, are pale white, red haired people. Not black. So they should be cast as what they are. The most egregious and lazy as fuck examples, are "Domino" and "Starfire". At least they KINDA tried with the outfit of Starfire, but the thing is, it was more important to them to show that "SEE WE HAVE A BLACK WOMAN", than it was to be true to what the character actually is: IE NOT a black human. Starfire is a goddamn alien, with goldish/bronze skin, red hair, and glowing green eyes. NOT a black chick in a hooker outfit, with a shitty pink dye job.
Domino honestly blew me away, because they actually bothered and put in EFFORT for Deadpool to look like Deadpool, and Cable to (mostly) look like Cable. But Domino? It's like they didn't even look at the comic. She's just some black chick, with a black accent, and an afro, and a weird little white loop around one eye. Yes, she vaguely has "luck powers", but her look is the height of Hollywood laziness. In BOTH cases, they could have cast a black actress if they really wanted to, but for god's sake, put them in MAKEUP, and at least TRY to make Starfire look like a bronze alien, and Domino look like a stark white woman with a black eye patch, and ZERO afro. It is pathetic when cosplayers with limited funds can do a spot on job, but Hollywood with millions and professional makeup artists and costumers, can't or won't.
And for the record, I'm a stickler even for crappy casting among "white" actors. It was lazy as hell to cast a brown eyed, brown haired woman as Jean Grey. It was lazy as hell to cast a blonde as Mary Jane Watson and then dye her hair. And then ironically cast a redhead, who by the way would have made a better Mary Jane in the first place, as a (bleached) blonde Gwen Stacy. It even boils down to lazy little shit, where it's obvious they're not even paying attention or just don't care, where they have, say, a brown eyed boy, playing the child version of blue-eyed Robin Williams' character. They do that a LOT in movies, with child and adult versions of characters with different eye colors, as if they just expect the audience to be too stupid to notice. Does it matter all that much? No, not really. But it's STILL incredibly lazy attention to detail, and lack of care in your own work.
But to reiterate my earlier point, as someone of "color" (though I hate that term) myself, if they want more "representation" of non-white/etc. characters in things, then MAKE them. It is lazy and insulting to remake a pre-established character, and shape them into what YOU want them to be, just to meet some kind of imagined quota. I'd be mad as hell if they cast Blade or Falcon or Cyborg as white, or asian, or arab. And I'd be just as pissed if they cast Superman or James Bond or Harry Potter, as a black actor.