There's a "town" (and I use that word very loosely here) in one of the ground missions I have done a few times at Lt. Comm. lvl. that has buildings that float (it may be the same one the OP talks about) and it also has a building at the back that is missing a couple skins on one side. I seem to always run smack into it everytime I'm looking for that last mob waiting patiently for me. Then I have to run sideways to find the corner so I can get away from it.
So, technically, I guess I hit a brick wall in that zone all the time.
More directly to the OPs question though, I think the obvious answer is time. As in, not enough to finish the content before selling it. They have been slowly filling in here and there for some time now, so I haven't seen the "bare brown ground and 5 box buildings and a painted sky with absolutely nohing else" for a few weeks now. I assume the lights, roads, and other details you mention will be there eventually, hopefully, maybe.
What is startng to bug me though is that I'm not sure any amount of simply "filling in" will make these missions any more fun. The basic structure just seems way to simple and repetative.
Time is a factor and I know that. I'm willing to wait a bit longer to see. But, I am feeling more unreasy all the time to be honest.
Eh, I've been away for a month and checked back in-game to see what's new and what's different. Even tho I waited thru about 10 mins of patch updates what I found wasn't much different. I went to different zones to where I have missions and also flew to different areas where I can get missions. It's all the same. The game is just too repetitive. Every mission, regardless of where it is, is just the same thing in a different skin. I've been playing this since jump start and I'm thinking I'll let my subscription expire in 2 weeks. It sucks. I was really hoping for a true-blue Star Trek experience. Instead, it's just an MMO with a Star Trek theme.