I can see your viewpoint in how, by trying to incorporate multiple tropes, each trope is left feeling incomplete. However, even though it's exploration isn't in depth, it depicts a beautiful sense of love in its truest form. A completely raw and selfish love (in the right way) that may people yearn for because it's so hard to find in reality which is why I think it's rated so highly
I love this story and personally think it is beautifully executed.
In my opinion, is more pointing out how absolutely toxic most yaoi stories are and how a proper relationship should look. It's a commentary on how we as people often tend to mistake accuse as love just because it makes us feel needed. This story is more about how you feel in the end and the beauty of being vulnerable with the right person than about the actual plot.
At the very least, I think my response is how others also feel who like me, have this story 5 stars.
I seriously don't understand how this story has such a high rating. It's literally trying using a bunch of tropes and barely weaving them into a coherent story. Not the worst BL I've ever read, but definitely close to the bottom.