Tag wranglers don't add or change tags, they only group and sort tags behind the scenes so that, for instance, if someone clicks on the "hurt/comfort" tag, they also get fics tagged with synonymous terms like "h/c". If a fic is uploaded untagged its going to remain untagged.

It is still going to require increasing numbers of volunteers as the archive gets bigger, and to make matters worse it's often hard to wrangle tags from a large fandom if you don't know the fandom.