I think Fairy type is a lot more fitting than say, Light-type. While English players have lamented that we have dark types and not light types, the literal Japanese would be more "evil type", with fighting types actually already representing their opposite as a type associated with justice. Whereas fairies are a phenomenon that aren't really covered by the existing types, and they have a number of Pokemon who fit the bill to retroactively become fairies.
Also, fairy was explicitly added to counter the dragon-dominated metagame, so there's that.
A super accurate rumour-mongerer who had many of their "predictions" come true today noted that Mawile will also be a fairy type (Mawile being based off the kuchisake-onna, the woman with two mouths), so Nintendo and Gamefreak haven't shown us all the fairies yet. It also hints that the idea of fairies also extends to myths of demons and supernatural phenomenon separate from ghosts.