In the past, people have criticized the "primarily opinion-based" close vote reason by saying "well, aren't most of our questions kind of opinion-based"? (This has definitely been a discussion on a number of occasions where questions were closed as "primarily opinion-based," and I can see it continuing to be a discussion in the future, especially as the site grows).
The current text of the Primarily Opinion-Based close reason is:
Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise.
Technically, I guess that does apply, but it's actually not all that clear from this why that's a problem or how the original poster should fix it.
The predecessor to "primarily opinion-based" was "not constructive." Ironically, while Stack Overflow and some other sites have moved away from this reason, I think that this close reason is actually a better fit for our site than "Primarily Opinion-Based." Here's the original text of that close vote reason:
As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or specific expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, see the FAQ for guidance.
To begin with, changing the name from "Primarily Opinion-Based" to "Not Constructive" would end the whole "well, aren't most literature questions opinion-based?" discussion and bring the focus back to improving the question to be a good fit for the site.
Secondly, it's actually not intuitively obvious why opinion-based questions are a bad thing on a literature site. This close reason is actually a lot more specific as to what the problem is: the fact that "discussion questions" aren't a good fit for a Q&A format.
Third, it's much more specific as to what kinds of questions this applies to: questions that would tend to lead to debate, arguments, and discussion rather than evidence-based answers. (Obviously, the kinds of things that constitute valid evidence on our site are different than what constitutes valid evidence on, for example, Stack Overflow or Math Stack Exchange, but we can tweak the message a little bit to reflect that fact).
This can be modified to fit our site by tweaking the wording. For example, we could do something like this:
As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by quotes, textual evidence, contextualizing information, facts, references, or specific expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. While good literature questions may be somewhat subjective, it should still be possible to construct answers that can be defended with evidence and convincing arguments; please edit the question accordingly.
The wording of this is hardly perfect, but it seems like a good direction.
Should we replace "Primarily Opinion-Based" with "Not Constructive"?