I do find it odd that readers are presumed to be uncritical. We've democratized the review of restaurants, of hotels, of music. What's so different about reading? Restauranteurs spend tens or hundreds of thousands of dollars to realize their dream. Chefs devote years to training, and toil over hot elements to prepare food under stressful conditions. Servers works their asses off every night to make the meal of patrons a pleasant experience. And yet people won't hesitate to give a ramen noodle house a two star rating.
The genre in question here might be confusing the issue. SFF skews young. And it has fans. Most fiction doesn't. Most people pick up a book on a recommendation, or out of curiosity, read it, feel it was good or bad, cast it aside and move on. At this moment, there are thousands of people reading Gone Girl poolside in Mexico. I doubt more than a fraction of them know who Gillian Flynn is, or care. And I doubt more than a fraction of them would care if someone in the deck chair next them commented that they hated Gone Girl. It's just a book.
Fandom has its merits. The enthusiasm. The shared community. But it has a bad side. The defensiveness. The hostility to those who break rank. The resentment of outsiders and those who don't share their enthusiasm.
Also, and it sounds almost quaint saying this, there was a time when professionals wrote reviews. Paid professionals. In newspapers. And that's how people learned about books. And the reviews were sometimes negative, sometimes positive. Judgements were made. That stance of the critic - an expert with no skin in the game - was once valued. Now, we place no value on it. It smacks of about the very worst thing a person can be in this day; elitist.