I've heard the ending of the novel sucked too, so this one might've been doomed from the start.
The rushed endings plague so many good stories, but I feel like it's usually because the artist/author aren't the ones to make the decision about when the series ends. They might have a whole season planned out and then the publisher is like "haha oops we're dropping this" and they have like 2 chapters to wrap things up. It drives me nuts but it must be incredibly frustrating for the creators.

I've seen so many good stories to end exactly like this, rushed with confusing ending (+bad translation) while other stories with terrible plots are getting dragged into 200 chapters and more, what's going on? Do these artists hate works they picked to draw or were they forced into it? Maybe because it's shounen ai and it actually have good plot with no rape and SA it's not that popular since we all know what stories selling most