Table tennis players struggle against China in major tournaments

They are ranked number one in the world in mixed doubles, and since they even beat the world number one pair, Wang Chuqin and Sun Yingsha, to win the WTT Finals, I thought it was a huge achievement.
Strangely enough, in the Olympics, World Championships, and Asian Games, the Chinese players almost never lose to Koreans.
Even in the Hangzhou games, the Chinese women's doubles team got lucky when other countries were unexpectedly eliminated, helping them secure the gold medal.
While the WTT Finals seems like a major tournament, it feels like winning at the Asian Games is even more difficult.
Even the Lin Shidong and Kuai Man pairing they beat yesterday is an opponent they have already defeated in the WTT.