I noticed that here on MSE, there's an unofficial policy of closing questions, especially unanswered questions, about deprecated or removed features of Stack Exchange. From what I can tell, this has several advantages; for example, unanswered questions about such features can no longer be answered reasonably, so it makes sense to remove them from the "unanswered" list by closing them. Also, this appears to have been done for many years, with such closures being under the "off-topic" close reason, and older ones done under the old "too localized" close reason.
Generally, when I come across such a question, I opt to use a custom off-topic close reason with a comment, such as:
I'm voting to close this question as off-topic because the concept of "accept rate" has long been removed from the system.
I'm voting to close this question as off-topic because the "tagged" list on the right has been removed many years ago.
I'm voting to close this question as off-topic because it's no longer relevant as moderators are now intentionally restricted from suspending users from longer than 365 days.
In most of these cases, including all of the above, the question does get closed as off-topic, but most of the time it's for a different reason:
The problem described here can no longer be reproduced. Changes to the system or to the circumstances affecting the asker have rendered it obsolete. If you encounter a similar problem, please post a new question.
I believe that this close reason is only intended for reports of problems that are ephemeral or user-specific, and the answer to that question would not help other users, and vote accordingly. I don't believe it's for questions about deprecated or removed features whose answer would have been helpful to others back when the feature was in service. But others generally close for that reason.
Why is this? Is my definition of the close reason wrong, or are these close voters wrong? Should we even be closing these questions, in your opinion?