Why do China people accept western fantasy, and westerners don't accept China's fantasy Xianxia?

Your understanding is reversed. It is the modern west that tells stories, makes movies and plays games at a higher level, so western fantasy is more popular. In the past, when terms such as magic furnace, crying planet and the fountain of life frequently appeared on the posters of various game magazines, the carrier was not the fantasy theme of the West, but the story of the game was well told and the products were well made. Similarly, Jackie Chan, Bruce Lee and others punched and kicked on the big screen in the west, not because of the fantasy Xianxia theme, but also because the story was well told or the products were well made. Fantasy or Xian Xia, they are just carriers, not the theme itself. People who often write novels (with certain experience) should know that the carrier itself is a means to attract the audience and an important basis for setting the specific temperament and world outlook of your story, but in the final analysis, the carrier is only the carrier, not the core content, not to mention the theme. Journey to the West has been popular in China for so many years, not because it is a fairy Buddha novel, but because it tells a good story. The Lord of the Rings is popular all over the world, not because it is a fantasy novel, but because of its huge and exquisite world outlook, gripping heroic image, nuanced story and exquisite writing.