Not sure as to how you are using the word PC in this context, but the diversity on the show seems to more accurately reflect the population I see everyday, in fact there maybe a little to much emphasis on the amount of fairer skin colour given the predicted future demographic mix of the world.
I think after all you're right. In fact you don't have to go to future; there are places, mainly cities, that are already highly diverse, including Toronto where I lived for over two decades during as since which it has changed a lot.
"Too much emphasis on the amount of fairer skin colour"?
Ha, right!! Watched any Bollywood flicks?
...
What always fascinates me about science fiction generally as a genre is its contention that despite the imagined phenomenal technological advancement that is always exhibited it is still in the hands of humans that have not evolved one iota and that the handgun and rifle in form factor and capability hasn't changed much at all; the bad guys can't hit the side of a barn but the hero is always right on the money.
...
Yeah, bad guys in particular a terrible shots regardless of the era.
...
The most interesting thing about The Expanse from my point of view is the class politics and even here the political motivation of a rebellion by the Belters is depicted as nothing but a criminal enterprise, the great unwashed led by nefarious leaders as a front for felonious material gain.
It does seem though, that the "great unwashed", with ever the legitimacy of their complaints, are easily corrupted by sociopathic megalomaniacs. Americas ought to recognize an example close to home.