Reasons The Book(s) of Enoch wasn't/shouldn't be accepted as inspired canon.
Historical and Internal Inconsistencies
1) It is impossible to determine if Enoch, who lived close to 6,000 years ago, actually wrote the books, or that it was a much later false writer, a Pseudo Enoch, writing under the name of Enoch. If this were the true Enoch, his writings would pre-date Moses' Torah and Job's book by possibly 2000-3000 years, and would have been close to 1,000 years old when Noah carried it on the Ark to preserve it from the Great Flood.
However, most scholars agree that the earliest date of the earliest parts of Enoch is no earlier than 300 B.C....leaving a supposed undocumented of up towards 2,500 years where there is no historical account of the existence of this supposed book written by the original Enoch.
In comparison, the gap between when Moses lived, however, and the first known reference to the Torah is only about 300 years.
2) It was never canonized by the Jews into the Tanakh. (The O.T.)
3) While it was known by many early Christians, and considered by some, it was rejected by most. Of the pre-Nicene church fathers, only Tertullian considered it. Of the post-Nicene fathers, only Augustine considered it, but had concerns of parts of it.
4) The RCC/EO churches both before and after their split; and even the early English Bibles and first 1611 KJV bibles who did include additional 'Apocryphal books' as historical writings in their Bibles, never included the BOE.
5) The earliest full copy of the BOE is dated to the 18th century A.D.....nearly 8,000 years after the patriarch Enoch supposedly wrote the BOE. Fragments have been found dated to the 1st century B.C. in the Quram caves, but those fragments weren't complete book(s), only about 6 verses out of 2 chapters....whereas the full modern-day BOE has 108 chapters. The Jude and Peter quotations, supposedly from Enoch, are not found in any early Enoch manuscripts; not until the 18th century A.D. version arose do they appear.
6) If it was truly written by Enoch the patriarch, it would predate the rest of the Tanakh (O.T.) by thousands of years....yet not one O.T. writer mentions this book, or mentions any writings from Enoch to be in existance. The Book of Enoch was missing from human reference for thousands and thousands of years....yet Isaiah tells us in 40:8 that "God's Word do not fade away". Enoch took a very, very long vacation if it was truly written pre-Flood. Then, to compound things, when it did should up circa 200 B.C., it disappeared again for roughly 1,500 more years. It 'faded away' twice!!
7) Enoch chapter 6 lists 19 angels by name, as the ones who lead the rebellion and the fall of man. Enoch chapter 69 lists 21 angels by name, as the ones who lead the rebellion and the fall of man --- and most of the ones listed are inconsistent and completely different than what was given in chapter 6.
8) Enoch chapter 7 teaches that the giants, who were created by Angels mating with humans, were 450 feet tall! That's as tall as the Washington monument, and over half the length of the titanic. That's 10 times taller than the largest known dinosaur skeleton ever found. How could human women birth creatures of this size?
9) Enoch chapter 71 teaches that the Sun revolves around the Earth, and that the Sun and the moon are the same size, and that the sun shines only 7 times brighter than the moon!