I don`t think anybody particularly cared about John just like, no matter what the media says, nobody really cares about Cyborg. Still, for the sake of discussion, it could be argued that John has some character development and feels like a valid character and not a token. The focus of the character is on him being a military man, a soldier. Never once he was shilled as "the black green lantern". Believe it or not, the lack of shilling on his racial attributes makes a difference. It`s the same for strong female characters... when the focus is on who they are as characters (personalities, conflicts, issues) and not on their sex you get far richer and interesting characters. Focusing on shallow attributes produces shallow characters. Diversity is been a thing for decades in comics, anime and movies. It just wasn`t the marketing selling point. Blade was not the "black vampire hunter" he was just this cool vampire hunter, Sarah Connor and Ellen Ripley where not these "strong female leads" even though they totally where (and it was well earned).
BTW everybody knows the hot couples of the justice league, the ones people actually cared about, where Green Arrow and Black Canary and Batman and Wonder Woman.