I think I'm a bit late here but I'd love to put in my opinion about this.
I don't think anyone would complain about a video not having a narrative unless it was called to their attention that no narrative existed. If the core of the music video is the synchronization of sound and visuals, then a video like "Euphoria" can still be enjoyed because the combination of minimalist graphics, characters displaying melancholy and decorative elements fit with the melancholy of Frou Fou's "Must Be Dreaming." MADs also fit here because a concept may exist except chances are the viewer can't understand Japanese and won't be able to establish a plot inside all the pretty graphics.
"Euphoria" is mentioned because I feel it is the biggest example of "mood over matter." It means that a mood can be conveyed without the aid of concept or narrative. With this particular AMV, the song vibrantly gushes melancholy and a hint of romanticism with heavy orchestrations and basic melodic structure. At the same time, the choice of anime (RahXephon) fits the theme perfectly even if its plot is way more developed. Scene selection is boiled down to shots that feature characters that aren't happy (or fit an ironic or surreal context if they are). The real kicker, though is if you close your eyes when listening to the song, or watch the anime, the feeling you're left with is almost identical. Koop adding a minimalist visual flare to everything was the perfect compliment, so a concept wasn't needed. When the video's over, if you feel a touch of melancholy, then that video was a success.
Now since something was being communicated, it wouldn't call attention to the fact that there generally is no plot to it. If the communication is being shared with someone who is unsympathetic to it, then they won't think there's a concept because they can't relate to the emotions brought out by the video.
So, I generally disagree with any and all who say a video without a plot is bad. Film, music video, or any form of art is a personal reflection of a supposed reality, and if that can't be communicated, then a video is just an effects demo.

