The most impressive entry in the annals of Jiang Cheng behaving like a reasonable human being is probably his response to Yanli leaving Yunmeng and marrying Zixuan. This actually makes a lot of sense to me because
a) Yanli getting whatever she wants is a priority
c) Closely related to b), he cares a lot about social and familial obligation; he probably is actually capable of thinking the situation as gaining a brother-in-law of dubious but still extant value rather than losing a sister. Yanli has a brand new job with an attendant set of obligations and priorities as Young Madame Jin, but that doesn’t at all stop him from thinking of her as his person. He automatically punts Jin Ling to the top of his priority list despite the fact that Jin Ling is not just a Jin but the Jin. Jin Ling is the heir to a different sect but still gets to give nonsensical orders to Jiang Disciples and has access to Zidian.
All of which to say I STILL maintain that the entire plot could be fixed with an intricate web of matchmaking (thank you Nie Huaisang) that does not make anyone learn and grow as a person but does force several characters to expand their mental web of “people I am responsible for” to basically everyone on the map.