All successful SE sites are basically focusing on a problem that someone has, and tries to find a solution by phrasing it as a question and applying answers as solutions.
This was originally established on Stack Overflow and the entire system was optimized for that use case. For example, upvotes mean that the answer is a good one, downvotes might mean that it is incorrect or dangerous, and the accepted mark indicates that it is this particular answer that solved the askers' problem. And it worked great.
The concept was afterwards copied to areas other than programming, and it was mostly successful exactly in areas where the question is in fact a problem to be solved. To name some examples:
And it worked great there, too.
What I'd especially like to point out to here is example #3. As it was posted on the blog post, it was an experiment with subjective questions, since raising children clearly has to be subjective. The experiment was seen as success, albeit having both subjective questions. It is my opinion that it was successful because it had problems to be solved phrased as questions, and solutions phrased as answers. That was enough to beat the subjectivity issue and make a good Q&A site.
What I'm arguing here is that the main problem of this site is absence of a problem to be solved. I mean really, what problems do we have that need to be solved using a Q&A site for Science Fiction.
The only common problem I can think of is What to read/watch next?, which obviously led to a big number of recommendation questions, later slightly disguised as list question. And the main trouble with these questions isn't objectivity at all, some of them aren't even subjective. It's the fact that they don't have an answer - they are open ended.
Gilles's analysis: A first look at questions so far shows us that list questions are so far most common. But it also shows us that there are more than half What do I read now? questions. (list, online resources, favorite X, identification)
So, my question here is What problems does answering a question on this site solve? As soon as we find out that, we'll know for sure what questions are on-topic here or if this subject can be used on a SE site at all.
As it is now, it seems that most (or all) questions are either google-able trivia or hidden recommendations. I'm not really sure if an on-topic question for this site really exist as it is now.