If You Could Change One Key Plot Point, What Would It Be?

The Three-Body trilogy's narrative is nearly perfect, but I'm sure every fan had a few "what if..." moments while reading. Let's discuss — if you could change one key plot point, which would you choose?

The most popular choice. If Cheng Xin hadn't become Swordholder, deterrence might have continued for decades or centuries. But the question is: who's more suitable? Luo Ji can't live forever. A military figure from Space Force? How would the sophons react?

If Yun Tianming hadn't chosen to hibernate (letting Cheng Xin go ahead), or if Cheng Xin had committed suicide after learning his brain was launched — but then the entire Death's End storyline would change.

If Zhang Beihai hadn't stopped to wait for Blue Space — he might have escaped with a fully crewed human warship. The flame of human civilization would have continued in the cosmos.

If someone had proposed a real escape plan (instead of being banned), or if social consensus had shifted toward building Starship Earth instead of defending the Solar System — humanity might have spread across the stars before Trisolaris arrived.

Without sophons locking Earth's fundamental physics — humanity might have achieved a technology explosion within 100-200 years, even matching Trisolaris. But sophons also limited Trisolaris's own tech progress (since they're one-way and irreversible).

If Luo Ji, after realizing the cruelty of the Dark Forest, chose silence like Ye Wenjie — would he be assassinated earlier? Would the universe remain silent forever?

If the Singer had sent a message before deploying the foil: "You're exposed, we're cleaning up" — what would humanity do? Flee, fight, or wait in despair?

In the comments below: if you could change one plot point, which one would it be? Why would you change it? How would the story change after that?