The book of Enoch pre-dates the New Testament and coming of Christ. Judaism doesn't accept sequels to their cannon very well, they literally killed Christ for trying to realize their prophecy of a messiah. and early Christains saw the book as unimportant, and because it contradicts the world of Christ and early church teachings. It's a schism in the religion that fundamentally severs the otherwise consistency of the bible. Ive only done a bit of reading on how Ethiopian Orthodox reckons with these inconsistencies, but its an interesting concept for sure. and not unseen in other sects, who selectively enforce the word and laws God laid down. Some are just disagreements with catholic doctrine through papal commands, but others are legitimate biblical revision.
That's an invalid excuse. Not including it in cannon is not up to the personal feelings of men. To do so would be to blot out the word of "god". Clearly a violation of scripture.
Deuteronomy 4:2
Do not add to what I command you and do not subtract from it, but keep the commands of the LORD your God that I give you.
There are many more books not included in cannon.
Also Christianity/Islam is Judaism that accepts (certain) sequals. The likely reason they are not included is because of contradictions or embarrassing claims the christian apologists were not prepared to reconcile.
Religion is a scam.