On the latest podcast there was some discussion about rephrasing 'Not Constructive', I think 'Open Ended' is a suitable replacement that accurately flags why the question has been closed, without being too hard on new users.
How about this alternative:
"No definitive answer"
It would fit the whole debate side of things, but it would also take care of the list questions where one could argue "But there's no discussion for those. That's not a debate." And at the same time it doesn't sound as harsh (to me) as "Not constructive".
Someone else said it, and I think it's a great candidate:
Not a Good Fit
This question is not a good fit for Stack Overflow. It's open-ended, asks for a list of things, or is impossible to answer definitively and objectively. If the answer to your question starts with "It depends", that's a good indication your question is not a good fit for Stack Overflow.
It's important that no matter what verbiage is picked, we don't invent new reasons to close questions. The text should reflect that the question objectively meets the site's criteria (it's about a programming problem, it hasn't been asked before, it applies to more than just the asker); but doesn't meet the style of the site: (Q & A rather than discussion forum).
How about going straight to the crux of the matter with simply closing as
Discussion / list answers likely
(followed by the description as usual).
This is what we're really objecting to with this close reason.
We're keen to use that close reason for questions that are likely to cause unresolvable debate/argument or lists of alternatives, so I suggest
Too open to debate
Too often I find people using Not Constructive inappropriately for questions that should be closed for other reasons, so I think the current phrase is misleading some and needs to be changed.
Originally, Not Constructive was originally Subjective and Argumentative. Not Constructive is more widely applicable, but is still a little pejorative. We recently changed "[closed]" to "marked as [duplicate]", which maintains our principles and high standards, but is less likely to upset. Be strict, but be nice while you do so; this way people argue less. I think "Too open to debate" fulfils those criteria.
As it used to be 'Subjective', (until subjective became subjective...), how about
Yes; good idea, call it
The text given for non-constructive gives suitable information as to why the question was closed. It doesn't fit all situations, but you can add a comment to explain this.
If you change the text to Open Ended, this will also be incorrect in some situations, so you'd still have to add a comment.
I don't see the point in changing it.