Fundamentally, why is the global economy slowing?

The customary reasons which account for a slowdown in the global economy (inflation and rising interest rates, excessive debt, the bursting of asset price bubbles) cannot account for the current global econom ic slowdown . The other explanations usually suggested (trade war, Brexit) are not convincing. So what are the causes of the slowdown in global growth? An "old-fashioned cycle", due to the saturation of needs for investment and durable goods; The special situation of China, where structural problems are causing a major growth slowdown; Not to mention population ageing , which is greatly reduc ing global potential growth.