Robert Christgau, often known for his sharp and sometimes controversial reviews, has a few common criticisms across the albums he reviews unfavorably. Here are some reasons he has given for his less favorable reviews:

1. Personal Taste: Christgau's reviews often reflect his personal taste, which sometimes leads to subjectivity source.

2. Dislike for Certain Genres: He openly admits to disliking certain musical genres. For example, he has voiced his disdain for heavy metal, art rock, and progressive rock, which could negatively influence his reviews of albums from those genres source.

3. Derivative Music: Christgau is critical of music he perceives as derivative or unoriginal. He values innovation and uniqueness and often penalizes albums that rely heavily on established formulas without bringing something new to the table source.

4. Cheap Gimmicks: He tends to see through what he describes as "cheap gimmicks" in music. If he feels an album relies on superficial elements or gimmicks rather than substantial, quality content, he’s likely to review it less favorably source.

5. Subjectivity and Controversy: His highly subjective and sometimes contradictory perspectives can also be frustrating for fans and readers, leading to mixed reception of his reviews. This subjectivity plays a role in how he evaluates and rates albums source.

These insights can help explain why Robert Christgau may rate an album less favorably, often sparking discussion and sometimes controversy within the music community.