I think that you're thinking with your writer's brain, and this is very good. I think, constructively, this hobby consists of role-players and writers, and role-players might not think as deeply about this stuff as a writer would. Theme is essential in many things, as is conflict. Conflict drives good characters, and if your theme doesn't have conflict that drives a character to act, then the setting is stale and milquetoast.
So, having said that, I'll use my recent comments on Carnival Row as an example:
One could argue that the characters sell the story, so I think you have to work it from this angle: Figure out WHY the characters are so good in the setting, consider what OTHER characters in the setting might be good, and then apply the show's format to the new characters. These new characters would be the PCs. So let's take a look at the theme.
From what I see, that show is essentially about struggle against oppressive political forces, and by struggle I mean "succeed or starve". Philo has to struggle against his role as a seeker of justice in a racist, brutal constabulary, Vignette struggles to survive against an underworld organization while struggling to keep her people alive in a ghetto during a war, Imogen struggles against high society and fear of keeping her head above water amidst a social circle of brutal, judgmental mavens, and Agreus struggles to maintain relevance and self worth as a sort of civil rights icon in high society (a society that is racist against him).
Is it great that Philo and Vignette have a romance? No. It's a thing, but what makes it great is that it's fucked up, dirty, desperate, and hellishly complicated.
MY POINT: I think when you look at trying to "recreate the thunder" of a genre, the reason why the BSG games did so well is that so many of the players came on board wanting to RP putting up photographs of dead family, living in shitty bunkhouses with little privacy, and GAME RUNNERS were mostly smart to avoid giving people private rooms. They recreated the THEME, and thus the ensemble casts were mostly successful in bottling that lightning. IF YOU ARE NOT GOING TO RECREATE THE THEME then you're just creating an idealized version of the theme, which is at that point not really roleplaying within the setting's universe but an adapted one of your own making. At that point, it doesn't matter who or what you make as a character; you're not going to feel like you're walking around in that setting.