There can, in some cases, be a real difference between diverse characters and a diverse cast.
Jason Momoa's mixed ethnicity shows through to some extent in his appearance, regardless of what Aquaman is "meant" to be (Atlantean). So I see some diversity in the character there. But you can't tell Ezra Miller's sexual orientation just by looking at him, and I'd bet good money he's not playing a bisexual character. Gal Gadot is from Israel, and is Jewish, but she's not playing a Jewish character, and almost everyone simply sees her as white.
There are always nuances. Jews were not always considered "white" in this country, and there are some people who insist that they're not. But I don't think we're getting a very diverse JL here, except for Cyborg and, to some extent, Aquaman. We are seeing some greater acceptance of diversity in the casting process, since they were willing to consider a bisexual actor - but in my opinion that doesn't really translate to the screen.
I have very mixed feelings about Cyborg. I liked him as a member of the Titans. His insertion as a founding member of the JL always felt like a bad fit to me, like checking off a box. It subtracted from him his relationship to the Titans, which had been a key aspect of his character, but I don't think they've really developed a corresponding relationship to the other JL members at all. And his solo series simply hasn't impressed me; I find it hard to remember what's happening from month to month.
I completely understand the desire, when recreating the JL from its origin up, to include more ethnically diverse characters in it, and I think that's a good idea. (It could do with some more women, too.) But I think Black Lightning would have been a better choice. Many readers would remember his longer history with Batman and others - even if its status in current continuity was vague - and he wouldn't have lost something that many readers cherish (like Cyborg's connection to the Titans). I do realize there's some issues with Tony Isabella, but I still think he would have been a better fit.
But that's just me.