As one of the people who has probably spend hundreds of hours to collate lists to make fanlor pages findable so that there now aren't 8000+ orphaned zine pages not linked to or listed anywhere, it is my opinion that even if we can't automate it will still easier to add categories by hand through the backlog than having to update lists by hand for eternity...
ETA: Actually I think having things in lists would probably still be useful (because you can potentially organize more info in them than in a category listing) but they certainly would be easier to update if for example for the Supernatural fanzine list you could just go through the category showing SPN fanzines and then add details from the pages listed there to the "List of SPN fanzines" page rather than having to go through all pages that link to SPN to pick out the fanzines by hand.
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ETA: Actually I think having things in lists would probably still be useful (because you can potentially organize more info in them than in a category listing) but they certainly would be easier to update if for example for the Supernatural fanzine list you could just go through the category showing SPN fanzines and then add details from the pages listed there to the "List of SPN fanzines" page rather than having to go through all pages that link to SPN to pick out the fanzines by hand.