I think they're unpopular only in theory at the moment. I think people here are more bitter that "OMG EZREAL LUX MF GOT MORE SKINS! RAGEFACE!!!!" and not actually giving them any credit as real skins. I mean, they are basically 750RP skins in terms of design (since they simply remodel the champion, and reuse particles and animations), and I also understand the pricing of 1350 if you don't own the original skins too. But I think most people here don't consider that and are just hating them to hate them, even after Riot corrected the pricing if you own the original.
I personally love the idea of them, and I think the skins do look super adorable on like Lulu and Soraka. I'm probably going to grab a couple of them at some point, and I think a lot more non-vocal people on the boards, and even off the boards will pick them up too. I foresee them being successful, and I'm kind of interested in knowing what the future will hold for Variant skins...