[[The Book of Yashar (Jasher), or “the Upright Record”is not Canon, but was referenced at least twice in Canon Scripture. Nothing I have seen so far contradicts the Canon Scriptures, and it explains things that are not explained in Canon Scriptures. For example: Cain’s offered “the inferior fruit of the ground” (Yasher 1:16) and that is why his offering was rejected.]]
It’s not Canon because it is not inspired by the Holy Spirit.
You can view it as that is what people thought at the time it was written so you view at as historical text but not scripture
Cain’s offering was not rejected because it just inferior .It was rejected because it was inappropriate .
God was trying teach them that the penalty for sin is death.
Something has to die to cover that sin. Cain instead brought the work of his own hands and that is why it was rejected. The work of your own hands will never cover your sins.
The sacrifice is a picture of Messiah dying for the sins of the world .
Then why are there grain and drink offerings? I would trust documents copied and preserved by the Essenes in the Dead Sea communities over some speculation by latter day preachers. Not bringing your best to offer is what is inappropriate. Cain was a farmer. He should have brought his first fruit.