Things on the Stack Exchange network change over time, as they should.
One relatively recent change was that made to the workflow in the "Reopen votes" review queue, when a reviewer chooses the "Leave closed" option. In such cases, we are now presented with a "Why should this question remain closed?" pop-up, in which we can either select a close reason different from the original or choose "Original close reason(s) were not resolved." This is a very positive change, IMHO.
Also, over time, new close reasons are added and others are removed; this is also a sign of a healthy, dynamic community.
But what should reviewers do with questions closed for reasons that no longer exist?
I recently reviewed this question, which was closed for the following reason:
Questions asking for code must demonstrate a minimal understanding of the problem being solved. Include attempted solutions, why they didn't work, and the expected results.
This reason was removed some time ago. In this case, I felt that the question was still not really fit to be reopened and chose to leave it closed with that original reason. But, shortly afterwards, I started to think about whether that was really appropriate. For sure, the question itself has not been improved (or changed in any way since its closure) but is it really the case that the original close reason has "not been resolved"? After all, the community decided that that was not a 'valid' close reason – so has the issue been 'implicitly' resolved?
What should we, as reviewers, do in cases such as this? (Particularly if no other, current close reason is really appropriate.)
There are other close reasons that have been removed in which the situation is a bit clearer: for example, on Stack Overflow, two reasons (essentially, "Belongs on Super User" and "Belongs on Server Fault") have now been removed and replaced with a more generic, "Not about programming." When reviewing posts with either of those old reasons, I have no issue with leaving closed but changing the reason to the new one.