China is communist in name only, if anything. Beyond the label, it was a revival of Legalism, which Confucianism once buried—now illuminated with neon lights.
Spengler would not see China's revival as the rebirth of a living culture because in his framework, Chinese Culture had completed its arc more than two thousand years ago and had long since hardened into what he called a "fellah" people, which are basically the remnants of a People after the Culture had died off. So modern China is post-historical in his sense.
He would read the Communist Project as a Western import. Marxism is a late product of the Faustian (Western) world, so China running on it means an ancient fellah-mass mobilized by a foreign political form rather than expressing anything inherently Chinese. The Cultural Revolution fits neatly here since smashing the Confucian inheritance was just clearing away forms that were already dead in a Chinese context.
The economic and military surge he would attribute to Caesarism and the inorganic energy of a "Civilization" phase, so what we see from China is more the brute machinery of mass and power rather than any springtime vitality of a young or emerging culture. So he would regard modern China as a force pretty impressive, but completely sterile as a cultural soul.
@CaribbeanRythms The Chinese really escape a lot of ire on here and I do not get it. Contemptible bug-men drones absent of human feeling. What makes it worse is that China is a country of fantastic beauty which is wasted on the Chinese.