I did not like the Librarians introduction at all. Specially because we don't need more factions.
I actually think they were long overdue. Looking at it, the notion that the American federal government - or heck,
any national government - just sitting back and not getting involved with the supernatural in any capacity is hard to swallow. They sit back and allow the White Council to dictate terms which, admittedly, has several centuries of capabilities on them, but still. There is no way, IMO, that individual national governments would not try and get involved in some way (whether that means fighting the supernatural, recruiting it, trying to suborn it, or even join it…) So there long needed to be some sort of organization in place that keeps trying to get Accorded Nation status but keeps falling short for some reason...
(In a Dresden Files RPG that I was running, I was about to introduce an overwatch organization called AEGIS (intentionally making a joke about SHIELD there) which was run by an Athena Grey who would naturally turn out to be
the Athena down the road... so I am a little biased toward them showing up, though.
)