You dont need to destroy Russia, but you can exhaust it to defeat. No more power projection and threats. In that way, you can defeat it without buring Russia to the ground.
The Chinese are not looking at what happened to Russia as a "World power" and "Second most powerful army" that is a western point of view. In the Chinese view, Russia is a second rate partner for them and economically beneath them, whose women are there for the sole purpose of being bar hostess in Asian KTVs. Russians for them are convenient as it allows them to rattle the western cages with out needing to raise a finger. Just look at their modernization, their military and tech modernization is more and more western in view and doctrine. They only keep Russian tech or weapons on cases where it is convenient or easier to just buy out than reverse engineer.