It's a little unfortunate that some people simplify these life struggles that many LGBT people face as a "boring, overused plot." Perhaps there is some truths as to why these tropes and plots are still popular today, it is still relevant in certain cultures.
I was thinking about it and my main complain about using those tropes/plots is exactly because they are still relevant. That is why when I read yuri I don't want to see it, because I have enough of it in real life. There is no point to throw it into a fiction too.
Well, to be fair there's one reason. Possibly the most important one.
Stories are about conflict. They can be all sorts of things, from trying to stop (or cause) the end of the world, down to leaving the milk out overnight and having to regretfully pour it out. What we see here is a conflict that would be easily recognizable in the culture it was created, by the people most likely to be reading it. Which is to say, not us westerners.
It's interesting how I was reading a blog post just the other day about reluctance some writers have to throw conflict in front of their characters, because they're your babies and how can you happily make their lives harder? But if you don't, you end up with a pretty flat story. I can identify though, as a reader. I don't want my babies to get hurt. But it's what a story needs, so what can you do?
I don't mind when some yuri bases its plot around it or make a more realistic take, but because about 90% of them is doing it, it became boring and overused, even if it is exactly how it is in real life. People want to read something light and positive to take their minds from sad reality.
Probably overselling that 90% a teensy bit. If anything, I'd say 90% of yuri is wish fulfilment with little in the way of serious opposition. And yeah, people want to read light and positive stories, but a diet of nothing but popcorn isn't going to give you good nutrition. Sometimes you need to read something with a bit of substance for good literary health. As Jefferson Airplane said, feed your head!