As someone who reads a lot of literary fiction, memoirs, and classics, yeah.

Not every work is a reflection of the author, but a lot of the more personal work is informed by their experiences.

A good example of this outside the literary world is The Dark Tower by Stephen King, which started me on this path. You cannot understand The Dark Tower without coming to some understanding of Stephen King, because in many ways, The Dark Tower is a portrait of a man's interests, his personality, and his worldview across his entire life. Everything in the Dark Tower is informed by some aspect of King.

Death of the Author is a valid way of interpreting work, but it's not a hard and fast rule. It's just a school of thought for critique and interpretation, and it's not true for every work ever published. I'm not gonna look up the life story of Stephanie Meyer or the latest YA author writing average fantasy, but when it comes to Shirley Jackson, HP Lovecraft, and Oscar Wilde, knowing their real lives and stories makes their work feel more "complete."

Your comments said you just want to read more difficult books so idk, do that?

Pick up some easier classics or modern literary fiction. Read an erotica as a reward for making it through.

If you write in library copies or borrowed copies, yes. But books aren't sacred objects and people who treat them as such are very silly.