"Killing a genre" meaning I can no longer watch shows of that type. Overexposure is what brought on the loss of ability to watch the genre. Of course this is all opinion and a personal experience, as it is for everyone with their preferences and dislikes. Again, order of exposure matters.
I'm not saying I'm any sort of expert on the harem genre. It is just my impression that LH packed everything into one and took it to that over-the-top level that then became so commonplace in the genre. Is it the first or the greatest or anything like that? I don't know. But my impression is that it took it the farthest, and for this reason, everything after it seemed irritatingly stereotypical, becoming unwatchable, thus "killing the genre."