BJ Alex is not a good example, caus Alex was a bully. That's easy to have a "character development". This story (in my opinion) is much more realistic and logical. I've read BJ Alex again recently and realised that they rushed everything. Like the make up was 1-2-3 back together (or actually together). Suddenly the relationship is perfect. That's not real, relationships are made of trial and error inside the relationship and outside the relationship. You make mistake, you realise you try to solve you make one again and the circle continues. It is how it is. But you grow from them and little by little you get better at dealing with them and on the way knowing your partner even better. This story portrays is so well. In my experience and the one of all my friends and family: talking about what bothers you does not immediately resolve a issue, it's just venting out while knowing it might happen again but you just go with it. (Unless it's really something that crushes you, then yeah that needs more help).
I know I can't really make a perfect comparison between the two and your right, its easy to show character development when you start off so bad because theres nowhere to go then up but what I liked from that story was that both of them grew not just one. Dong-gyun learned to love himself and not take abusive behavior from anyone and stand up for himself, Jiwon also grows and learns to deal with past trauma and how to treat a partner and relationship in a healthy way. I think I mostly wish Jungwoo in this story would grow a bit more and also learn to love himself and be self sufficient even if it's in small ways. I do wish there was more communication between them tho but misunderstandings are a classic in the romance genre. but if I could change one thing it would just be that Jungwoo gets a consistent therapist or at least one good friend independent from his relationship that serves as a support system to keep him from spiraling when Youngmin can't and just in general help him take baby steps into the real world.
I love this with all my heart butttt... there doesn't seem to be much character development or growth. It seems like time and time again they fall into the same traps without much resolve. it's pretty much just them going back to each other once the withdraw symptoms from each other are too much and they admit they were both wrong but don't really do much about it. I know having a healthy relationship is almost impossible in yaoi land but I really wish they would heal themselves more and learn to be independent so when they do get back together they're together because they love each other and WANT to be together instead of this scenario where its either be together or self destruct. BJ Alex did a great job of this where the character both grew to accept and love each other AND themselves while growing as people when they were apart. tbh tho I know I'm way too invested in this but I can't help it I love this so much its so cute yet sexy.