I've been on Goodreads, but not in a while. So, take my opinions with a grain of salt.

- First and foremost, protection from review trolls. Goodreads star ratings are influential, impactful, and unreliable.

- A flexible yet coherent system for grouping books. Maybe multiple systems. For instance, I have trouble finding hard sci-fi books because most sci-fi has fantasy elements and hard sci-fi isn't the most popular subgenre. Some books are genre-benders. Sometimes a "subgenre" is better characterized as an intersection. Maybe something tag based, but the tags are categorized.

- I'm not interested in popular reviewers. I'm interested in reviewers who like the things I like.