Ye Wenjie is too emotional. Which is a bit of a flip side of the same coin: she is presented as lacking in logic and ruled by emotion, much like Cheng is throughout Death's End.

Spoilers for Dark Forest and Death's End follow:

Cheng in Death's End makes several decisions:

1) As Swordholder she balks at transmitting the coordinates of the Trisolarians into the universe. Humanity is corralled into Australia and Mars to be starved until their numbers are more manageable by the Trisolarians. I vividly remember the flowery prose of how she just couldn't consign so many Trisolarians and Humans to death and that surely the Trisolarians would be the better choice. The prose is rather condescending of her choice. One hopes it's merely the translation.

2) One of the clues given to Cheng by Yun involves faster than light propulsion. However, it leaves behind evidence that can attract a Dark Forest attack. Cheng has Wade continue researching the propulsion but maintains the final say-so on if they proceed. The human government discovers the project and the choice is either armed conflict with antimatter bullets that'll cause a lot of death and destruction or to stand down. Her choice is to stand down and avoid conflict, this directly results in all of humanity (with the exception of her) that exists in the solar system being destroyed in the inevitable Dark Forest attack.

3) Cheng finally gets to make a "moral" decision and leave the pocket universe to try to ensure the universe cycles into another big bang. It is interesting because technically the decision is almost certain to not work: it depends on all the other residents of pocket universes also leaving and reentering the dying universe. It's almost like at the very end Liu Cixin gives this tiny concession so no one can be like, "Bro, what's your problem with women?"

There's an entire thing at the start of the book where Liu Cixin spends an inordinate amount of time describing how effeminate "peacetime" men are. It gets creepy and quickly becomes obvious it's a very personal takedown of Korean and Japanese men. Later, during the bunker era, Liu Cixin spends an equally inordinate amount of time singing the praises of tough, masculine men during a time of hard decisions made in the name of survival.

He just continually uses Cheng's empathy and (rather unbelievable after her mistakes as Swordholder if I'm being honest) naiveté to kill huge swaths of humanity. It's fairly obvious what his opinions are.

The whole message of "we need people to make tough (borderline genocidal) decisions for the survival of our people/race" is weighted so immensely, you get brow beaten by the author. It moves well beyond the norm for even military sci-fi, much less hard sci-fi.

EDIT: Also Luo's arrest after he steps down from being Swordholder for crimes against a star system that wasn't even known to be inhabited at the beginning of Death's End is ... the most blatant and ham-fisted critique of Western Woke-whatever I've ever seen. It's good, don't get me wrong. But it's just so hilariously obvious what Liu Cixin's bone to grind was.

I find it difficult to give him a pass for writing "bad things" about the Cultural Revolution when he ends up at the same fascist conclusions.

I'm not saying not to read the book. I don't actually regret reading the entire trilogy. It's got a certain nostalgia for the clumsy hard sci-fi of the 70s. However, I don't feel the trilogy does much to really extrapolate the Dark Forest theory so much as co-opt it to validate a set of ethical and political beliefs.