"Jude’s quote is not the only quote in the Bible from a non-biblical source. The Apostle Paul quotes Epimenides in ***us 1:12 but that does not mean we should give any additional authority to Epimenides’ writings. The same is true with Jude, verses 14-15. Jude quoting from the book of Enoch does not indicate the entire Book of Enoch is inspired, or even true. All it means is that particular verse is true. It is interesting to note that no scholars believe the Book of Enoch to have truly been written by the Enoch in the Bible. Enoch was seven generations from Adam, prior to the Flood (Genesis 5:1-24). Evidently, though, this was genuinely something that Enoch prophesied – or the Bible would not attribute it to him, “Enoch, the seventh from Adam, prophesied about these men…” (Jude 14). This saying of Enoch was evidently handed down by tradition, and eventually recorded in the Book of Enoch.

We should treat the Book of Enoch (and the other books like it) in the same manner we do the other Apocryphal writings. Some of what the Apocrypha says is true and correct, but at the same time, much of it is false and historically inaccurate. If you read these books, you have to treat them as interesting but fallible historical documents, not as the inspired, authoritative Word of God."

( https://www.gotquestions.org/book-of-Enoch.html )