I think the author knew just the general outline of the story but not how to execute it. Like mc's decision to get back with seok-il came outta nowhere. Apparently even their other story is weirdly paced. We expected too much from the author i guess ┑(￣Д ￣)┍
I mean, it's no worse than the majority of this genre where the "main couple" consists of characters that last saw each other decades ago when they were toddlers, and one thought the other was a girl. Or any abuse in a relationship being swept under the carpet, because in yaoi law they have to end up together! I think given the characters aren't teenagers and were in a long term relationship, we expected something different and better though.
I can not tell if this manga is badly written or if the author is just trying to install a suspense for later. Like, the plot's really too fast, it's weird.
Anyway, the more we progress in the story and the more Woohyun develops a toxic personality!