That all depends on how you look at it. I've no idea why people would consider a black bond too unrealistic, unless, perhaps, ya know, they think Bond character exemplifies or is some kind of bastion of whiteness.
And if it was considered a cultural statement, then isn't it time that statement was made?
But yeah, Elba is too old. He'd be lucky to get 2 films.
I take this discussion entirely on face value -- which is to say, I'd love to see Elba as Bond. Might actually interest me in the series, to be honest. He's a formidable talent, so I'm firmly in the "why not?" camp.
On the other hand, if you were to approach it using the same rules as the screeching far-left camp, then it's ignorant, bigoted, and racist to say that there's nothing different between two people just because one is white and one is black.
The reason for this being that since Bond is now a black man, what does his ingrained history of the "Black Experience" -- including being forced to face systemic racism his entire life; being oppressed, opposed, and micro-aggressed every single day, and made to feel unsafe in a society that has never been "for" him -- bring to the table?
As a character, those things
must inform his choices, beliefs, and reactions.
And therefore he simply
cannot be the James Bond of existing canon. Unless you go the route of 007/James Bond being a codename, and not an actual individual. (I think that approach is just fine, to be honest.)
That's the only thing I can't wrap my head around when it comes to these matters. Personally, I don't care. Cast whoever, as long as it's good. But don't clutch pearls and scream about whitewashing and then turn around and do the same thing with a different skin colour while
still claiming that X ethnicity could
never understand the experience of being a POC. Either your experiences matter and inform your character, or they don't. And if they matter as much as the "SJW" set insist, then the character will be fundamentally altered far beyond mere aesthetics by such a change.
In that case, surely the best option is to create a new character instead -- much like the (excellent) Miles Morales Spiderman.