It is said that Taoist tantras were all royal feng shui masters in ancient times? Is it really that good?

I think it's true. Yuan Tiangang and Li, for example, are good at national luck and require high attainments. Think about it. Ancient emperors were not idiots. Qin Shihuang unified the six countries, Han Wudi defeated Xiongnu, and Li Shimin initiated the rule of Zhenguan. They are smarter than anyone. If these masters (Xu Fu, Yuan Tiangang and Li) had no real skills, they would have been killed several times. what do you reckon ?