now I am not exactly sure but are you trying to tell me that in a BL drama or whatever. The Two guys in the cover are not going to be the main couple that ends up together? Also I saw some Bl books bout 50-60 year old men fuc**** a 20 year old guy. So i'd argue that the Bl genre has its own couple of disgusting stories like that.
And about quality: Stories have quality if the writer knows how to write in a way that is appealing for the audience. As such I can't really take anyone serious that believes that just cause a Story has certain tags the story is bad or good. Although Yes there are certain tags that have a lot more trashy storys than good ones.
Really just go on the genre and scroll through the pages. Every single Cover is basically the same. And the describtions are as similar and as Different as the describtions of any other genres.
I am not saying all BL is all the same but if you look at the Bl genre and then at the Shoujou genre for example, then you can pretty quickly see that most Shoujou and most Bl Titles have a lot of similarities with titles of their respective genre, while also having a lot of differences of similar kind. And while I didn't read any BL stuff or at least not enough to judge it, I can say that I read enough shoujou sh** to say, that it is definetly not unique and has as many cliches and predictable plots as the Harem genre does.