I think something I’ve often seen Xie Lian portrayed as/criticized for is his abundance of knowledge/lack of awareness of things but there’s never been any in-depth talk or mentions that I’ve seen of how smart he is as well. Of course much of Xie Lian’s attitude towards himself in terms of undermining situations, deaths, and other unfortunate happenings to himself and lack of awareness in that regard is because of his really bad coping mechanisms when it comes down to himself and his trauma, something of which was very repetitive and extensive to the point where he had to condition himself to a new lifestyle, atoning for what had happened to him and others, essentially. Never mind the fact that Xie Lian was then alone for several hundred years after the fact and had no one but himself and Ruoye (who is a grim reminder of his parents). When Xie Lian buckles down to tasks he has to do, he’s proven himself to be incredibly insightful, knowledgeable and hands on. He’s never called himself anything less than capable when it comes to his strength when asked to fight, even if he still turns it down. Rather than Xie Lian dumbing himself down, it’s more that he carries a lot of guilt to the point where it’s pointless for him to really defend himself. He’s also intentionally put himself as the blame for situations to save further grief (which luckily Hua Cheng helped him out with).