The martial techniques given by Xu Yi's system are ones that the Spirit Race doesn't have.
This is the advantage humans have to overtake them.
In fact, it's not that the Spirit Race hasn't tried to purchase or exchange for these martial techniques and spiritual skills from other civilizations.
Unfortunately, the current Spirit Race is just a small group that managed to escape, and their resources are very limited, so those civilizations aren't interested.
Not plundering the Spirit Race's people and resources is considered very kind.
So, when Ling Qi discovered Xu Yi's Body Refining Technique, she immediately sought out Xu Yi for a trade.
Moreover, the conditions offered were the best the Spirit Race could think of.
After all, the Spirit Race understands the value of these cultivation techniques.
If it were any other civilization, they probably wouldn't even trade with the Spirit Race.
There's no way around it; when information is asymmetric, losses are unavoidable.
