Adding to what OriginalGengar asked: Do you also not think that yuri is for a niche audience? Cuz it is.
Of course yuri is niche Late Night. Anime itself is pretty niche. But it sells if done right or if it is just a part in a bigger show. I have no idea where that "yuri does not sell" comes from. Of course it does not sell if the shows are shit. Look at Sakura Trick. The show had nothing but kisses. The humor was mediocre at best and the characters not all that interesting. Of course it would not sell. A hetero show would sell just as bad.
About the genre thing. Yes i think yuri should not be classified as a genre. It can be part of something but is not a genre itself. What kind of a genre would yuri be? it is always part of romance/comedy/etc.