Honestly, I think this was the perfect way to wrap up the arc and regarding the emperor never remarrying, unlike other people who say that the lingering attachment he has for his 'mother' is more than familial love, I honestly see Yun Ling or whatever his name was as an asexual aromantic cause I mean just think about it; he's never had any interest in anything involving 'love matters' and he might just go on to adopt an heir. Or maybe I'm just overthinking and he hasn't met 'the one' yet but what I do know is that there was no romantic interest from him to su luxia except maybe before he realized they were the same person...
This is just my opinion, I don't mean to offend anyone 😃