So we have this entirely new universe to play in. But we are never given any amount of explanation for the majority of that universe. Sure we understand the basic broad strokes, Alliance=big bad government, inner planets rich, outer worlds not so rich. But we never get an explanation (In series) for the whole Chinese thing or the mix of Western and Eastern influences, they are simply there in the background and we as the audience are expected to figure it out.
No, we're not.
We as the audience do not need to figure out anything, other than the broad strokes you mention, to understand the story we're being told.
If we so desire, we can dig in and discover that the Alliance is the Sino-American Alliance and the result of a merger of our present economic superpowers some centuries into the future. This explains why the characters occasionally curse in Chinese -- but at the same time, we don't need such an explanation. Hell, we don't even need to know it's Chinese. It's just as easy to accept that language will have evolved new vulgarities ("frak") and again, it isn't something that's relevant to the story at hand. It's texture. It isn't necessary to know it to enjoy what you're seeing; but it makes the world feel more real because the creators know it, and it helps them define the rules of the world in which the story occurs.
I guess another way to put it is, where is the difference in building a universe to play in, and just having it be distractions for the audience?
When it gets in the way of effectively telling the story.
To quote David Mamet, "Backstory is bullshit." As in most things, I think he's oversimplifying, but as in most things I think he knows that.
It's fine to have backstory that comes to light and informs the story. That's often necessary, but unless you're writing a mystery, should be kept to a minimum, since backstory becomes exposition and there's few elegant ways to get it across.
It's also fine to have textural details that enrich the world and define the rules by which it behaves, but which never need to be explained for the story to make sense.
The problem is when backstory/details need to be explained in order for the audience to follow what's happening, and yet the details themselves aren't actually important to the story.
I'll give you a quick example. I read the script for a Star Wars fan film in which there was a scene where the hero plays Sabacc. The Sabacc scene went on for five pages, because the writer had looked into the EU rules for the game and wanted to present a Casino Royale-style scene of cardplaying prowess.
Problem is, no one in the audience is going to know how to play fucking Sabacc. There would be no tension in that scene because no one knows what they're looking at. Now, if you got good coverage you could manage something in the edit just based on how characters react, but that's not going to keep the audience with you for five minutes. And yet the story was going to derail during this scene completely. There's no way for the audience to go along with it without having it explained to them but it would be unreasonable -- and unnecessary -- to detour from the story to present that explanation. It's nice you did the R&D, but no. Find another way to accomplish the plot point.
By contrast, do you know how to play the game in Firefly they were playing at the beginning of "Shindig"? "Plums are tall?" But do you need to? Does it have anything to do with the story? No. It's just a textural thing they're doing.
I guess the difference is -- is it a background detail, or a foreground detail? Be careful that you don't drag the background into the foreground when you don't need to. I want to punch the shit out of fantasy/sci-fi writers who include a goddamn glossary(!) in their books. Okay, you did a lot of work developing this, but that's for you, not for me. Don't beat me in the face with it.