Closing an issue does not delete it, and search will still easily find it.
In the example you mention the problem is more that nobody had the courage to say “no, we should not do this” – which IMO is correct response: if we had wanted that we could have implemented it that way from the start.
I am not at all worried that if we closed this and someone implemented it independently and we approved of doing so, we would collectively forget that there were other modules that would need to be updated.
I don’t see a downside to closing that issue, and I see two upsides: one less open issue in the tracker, and nobody has to make an explicit negative decision – we can just let the lack of interest imply that the status quo is fine.