Sarcasm is an adjusted stress reaction.

What Liz said. I think it's good to remember, as well, that neither Finn nor Poe was ever supposed to be part of the larger story. It was always going to be about Ben and Rey from the beginning, and Finn was just a comedy sidekick for Rey in the early drafts while Poe was meant to die in the battle of Tuanul and never be seen again (at least until Oscar Isaac talked JJ Abrams into letting him live instead).

So when LF saw how positive the fan reaction to Finn and Poe were, they had to do some fast retooling of Ep. 8 to give them an expanded role in the saga, which explains why at first glance it feels a bit tacked on and not as emotionally resonant as the Luke/Rey/Ben part of the story. That's a Doylist explanation rather than a Watsonian one, which I know is not always the most satisfying, but I don't think it's really got anything to do with Rian only being interested in the white characters.