First of all, the monarch of Chu didn't know how to appoint talents and pushed many talents to other countries. Wu Zixu is one of them. Wu Zixu's father and brother both died because of the framed by King Chu Ping. Wu Zixu fled to Wu to become a doctor in order to avoid being pursued. It can be seen that even if all talents come from Chu, Chu can't keep them.
Second, the military posts of Chu are monopolized by three clans, which means that all the so-called soldiers belong to these three clans. Even if these three families have been at war for generations, there is no guarantee that their descendants will be brave and good at fighting. Their monopoly on military and political power prevents other capable people from being appointed, and naturally there are not many famous Chu generals.
Thirdly, Wuqi once went to Chu to carry out political reform, hoping to change the status quo of Chu, but it was gone after the death of the king of Chu. Because after all, Wuqi touched the interests of some Chu nobles, who just wanted to surround Wuqi after the death of the emperor so that everything could be restored. The new monarch of Chu was too weak to punish excessively those who obstructed the political reform, so he compromised with each other. Even the appointment of outsiders is not given real power, and there will naturally be fewer stars.