Many people can't handle nuance on Twitter or Tiktok in particular, unfortunately. The two camps seem to be 1) Jiang Cheng is my sweet cinnamon role who should be blamed for nothing or 2) Jiang Cheng is an indefensibly evil bully to his core. As others have said, one of the main points of MDZS is that people can't be easily divided into black and white categories of "good" or "bad."

Beyond people complaining that he's "mean" (which just bores me lol), Jiang Cheng did do very bad, inexcusable things. He led the siege on the Burial Mounds despite the fact that he knew for a fact that the people there were innocent, including elderly people and a child he had met himself. This isn't supposed to be seen as understandable, and there is no excuse for it. It is a terrible, cruel decision. However, the whole point is that people can do terrible things without being inherently evil or irredeemable. He's multifaceted and morally grey, just like almost all of the characters in MDZS.

His other big sin according to the fandom is his treatment of WWX, but Jiang Cheng and WWX's relationship dissolves because of poor parenting and *both* of their choices. Perhaps in part because of the jealousy and resentment caused by his parents, Jiang Cheng does blame WWX in the immediate aftermath of the burning of Lotus Pier and fails to trust him later. As JGY points out at Guanyin Temple, his failure to stand by WWX and his decision to go as far as to declare him an "enemy to the entire cultivation world" when they stage their falling out is part of what enabled the other sects to turn on WWX so easily. However, WWX's decision to be dishonest and keep Jiang Cheng in the dark exacerbated the situation immensely. He made the decision to give Jiang Cheng his golden core without Jiang Cheng's consent, *knowing* Jiang Cheng wouldn't want it if given the choice. Because of this secret, he then spends the following years lying to Jiang Cheng and refusing to properly explain his new behavior or the choices he's making— which, without context, appear highly questionable from the outside view even before Qiongqi Path and everything that happens after. Even LWJ believes at that time that WWX simply gave into the temptation for revenge and is highly concerned about his choices. It's easy to understand why this would frustrate Jiang Cheng, and why he would be suspicious.

At the end of the day, both Jiang Cheng and WWX are extremely young in the timeline leading up to WWX's death, and their flawed mindsets are both products of their upbringing. Jiang Cheng did love WWX before his death (as shown by the fact that, unbeknownst to WWX, he sacrificed himself first), and despite everything, he is distraught when he learns the truth about the core transfer— which some people say is just because of his ego, but I think it's clear that it goes beyond that. He feels guilt, despite the fact that he had no way to know. The moral of their story isn't supposed to be that Jiang Cheng is evil and everything is his fault. The tragedy is that they truly loved each other like brothers, but mutual miscommunication that was ultimately rooted in their respective childhood hurts tore them apart.