This manga is SIXTEEN years old. SIXTEEN. Thats older than some of y'all reading this. And has over 10 volumes. Which no doubt generates a healthy profit for the author. Lets keep in mind there is absolutely no cohesive plot between volumes (unlike equally as long mangas like viewfinder, crimson spell, even sekkaichi hatsukoi to some extent) which means said author can do whatever tf she wants and still generate a profit doing so. This manga could have ended easily in like volume 5 should they have gotten together. But its still ongoing so gullible people pick up the magazine this is serialized in or buy the volumes in case they actually DO get together.
As long as this series keeps making profit. Senpai will NEVER say i love you and they will NEVER get together. Y'all love to forget the yaoi manga market is basically making porn and literally profits off straight womens fetishization of gay relationships. Most authors dont care about neatly concluding the story or developing plot. Its about the $$$$$$
Ok, so why ask the question if you're gonna answer it yourself?
Most of your reply makes no sense in the grander context, btw. Yes, we all know Yaoi is mostly made for heterosexual women, that still doesn't mean women like to see dysfunctional or broken relationships, like portrayed here.
Also, you say "most authors", but I'll just assume you haven't found the absolute gems out there, like Blood Bank, BJ Alex, Ten Count, Yellow dragon and Kashikomarimashita Destiny, just to name very few from recent years. The Yaoi market is as saturated as any other, of course not every work is going to be absolutely amazing.
Also, I'm definitely part of the "dropping this manga" camp. I started reading Koisuru when I was 12, today I'm nearly done with university. The story is simply not worth it anymore, imho.
I think you're forgetting yaoi is a type of pornography. For example, every single one of these volumes contains a sex scene - which is why people are BUYING this manga, because lets be honest - theyre not reading this for whatevers left of the plot. Also if readers disliked dysfunctional/broken relationships, why didnt they stop reading after the rape scene in volume one? Why continue reading? The reason is = sex - the whole reason this sells. For example - for every manga you listed is sexual in plot ie. Blood bank is about bdsm (one of faves), BJ alex is about broadcast jockeys, Kashikomarimashita Destiny is about mpreg. All of these although argueably have more a plot than THIS, are still all centered around the sex - which isnt neccessarily a bad thing but this is what SELLS the manga/manwha. Because lets be real - woukd you have read any of them if there was no sex in them?

Do y'all really think senpai is ACTUALLY going to say i love you???