Yuan Shao is the warlord of the northern region and the strongest warlord. His clan is always in internal problems, and there is essentially no unity. The sons compete with each other for succession, and the clan elders are stuck between Yuan Shao, Yuan Shu, and loyalty to Han. After all, the Yuan clan has the reputation of being loyalists. This reputation is most important to Yuan Shao, and he does whatever to keep that good reputation.
Because of this, he leaves the future of the clan in Yuan Fang's hands. Since Yuan Fang is the illegitimate son of Yuan Shao, he can do whatever he needs to rule. And Yuan Shao has decided to entrust the future to Yuan Fang.
As a character, Yuan Shao is full of hypocrisy because of his love for reputation. He doesn't have a lot of notable generals like Cao Cao does, but he has more troops, and that's what seems to matter at the moment (Guandu).