The specific claim you're reacting to is ... puzzling. I'm not sure that there's a fiction book in existence that doesn't have the author's voice and opinion in it. I suppose ghost-written books in the style of another author? But I suspect that's not what is meant.

Here's a stab at what this criticism actually means: the author is making it very clear what they think and narrowing the potential meaning of their work in the reader's mind. Very much a stylistic choice. Some writers prefer to leave their work open-ended and don't worry about interpretation. Some writers actively encourage readers to interpret in unusual ways. Others have very definite designs embedded in their work; some interpretations are objectively wrong.

A lot of people don't like the latter kind of author. I'm not sure why. I suppose because some readers get frustrated if they have ideas about a book, then find that their ideas were wrong and that they misunderstood the book. There's also a belief floating around that books never have incorrect interpretations, which makes no sense to me. But people believe it.

As for a fiction book with so much of the author's voice as to be obnoxious at times? Ayn Rand, obviously. I actually like her work a lot, but she sometimes forgets that her characters are characters and starts writing monologues in her own voice, instead of the characters' voices. At times she does this with characters who are ostensibly having a conversation, but the two sides of the conversation bleed together and you can't tell who's speaking anymore because their voices lose all differentiation.