At what point does prose become overwritten? (Looking at you, Whalefall)

Just finished Daniel Kraus's "Whalefall" and have mixed emotions about it. I actually didn't mind the fact that it was "just daddy issues inside of a whale" or that the whale itself felt more like a plot device, as some Goodreads reviewers put it.

What I do mind is that most of it reads like spoken-word poetry due to overwriting. I honestly laughed a few times because I couldn't help picturing someone reading it aloud with a cigarette in one hand and snapping their fingers with the other hand.

So my question is, at what point does prose in horror fiction become overwritten in your opinion?

Edit: To paraphrase a comment of mine, I don't think there's anything inherently wrong with overwriting as it's a personal opinion kind of thing. But overwriting tends to come at the expense of slowing the pace and robbing the reader of chances to use their own imagination.