I don't get any assignments, I am not allowed access to the last 8 levels, I have 15,000,000 credits that do me no good. Did the programmers wander off before they finished this game?
I don't think the game had a well-defined "finish" even when it was being more actively maintained.
Now pretty much once you've got 100+ levels and the Imperial tasks stop coming, there isn't much to do except keep things chugging along. When it was more actively maintained, there were the periodic events but there haven't been any of those in a long time, since about March 2014 I think. And for earlier there was a tantalizing "new levels available each Tuesday!" announcement but there wasn't follow-through on that.
According to the webpage at http://www.eurogamer.net/articles/2014-10-07-disney-removes-tiny-death-star-without-telling-the-developer the game is no longer available for new players from the App Store or via Google Play, so that's a sign that nothing will change in the future.
There are unreleased levels according to http://tiny-death-star.wikia.com/wiki/Category:Unreleased_levels but it doesn't seem like any chance those will be available.