Just read through the thread you linked. Everyone seems to agree that a very significant part of the issues in GitHub are of such a low quality that they could just be closed and that there needs to be some clean-up.
The question is now, of course, how this should be approached and who will do the actual work.
IMO, particularly @kisg 's comment included some very helpful, actionable ideas. And I think he makes a good point when he writes:
I think this is something where the community could help a lot, but the exact procedure needs to be defined and documented.