I know a few close reasons have been merged, but no longer relevant was useful, and now it's not here anymore.
What should be use in its place?
I'd say too localized:
This question would only be relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet.
Emphasis mine. Whoa man I can see through time.
Here we have another example of "no longer relevant": this question on SU.
The problem "solved itself", no accepted answer, nothing. It's a typical case of a "situation" which is no longer relevant. "Too localized" would be weird for that kind, really.
And yes, closing such questions has a point, because if someone comes with a similar problem, this existing question won't be of any use for him, and yet will be a living "duplicate".