What’s wrong with studying uncanonized books, such as Enoch?

There are several reasons the Book of Enoch not canonized!

First, we have no authoritative Book of Enoch; rather, we have documents that purport to be the Book of Enoch. It's pseudepigrapha.

Secondly, its calendar is indecipherable being only an agricultural calendar based on the sun, not matching scripture.

Thirdly, it contradicts the canonized scriptures and, honestly, could we have today a "book" written by a man who existed such a long time before the Flood? While we have evidence of some very ancient writings on tablets, few, if any, have been shown to have been written by anyone prior to the flood.

Yes, stories of Enoch circulated in Biblical times. He is even mentioned in Jude 1:14 regarding a prophecy from Enoch. But since Jude was written in the First Century CE, its reference to Enoch is most likely only expressed from oral tradition and not any "Book of Enoch" which is nowhere mentioned in scripture.