I think that when I've heard people talk about various vids not being "fannish," it's usually implying that the vid was less about love of the show/pairing/characters, and more about the whizzbang of snappy editing/effects/glossiness of the vid. It seems to be used as a distinction between older style (particularly pairing-oriented) vids, and newer ones that some people perceive as being more... professional?

It's not really a distinction I consider to be valid; I think the type of distinctions that seem to apply when someone says this vid is fannish, and that one isn't, have more to do with personal vidding styles and the evolution of vidding, in general.