The example list given just looks a lot like spam when you squint. It's a list of affiliate links to buy products, and there are many HN threads talking about the abundance of affiliate link aggregators being a blight on the web. The commentary does look useful, but distinguishing between good commentary and bad commentary is hard, whereas distinguishing between a site designed to extract affiliate commission vs one more about the content is easier.
The comparison given to the other results here is frustrating, I know, but probably not a valid experiment. All the major search engines change results based on the user using them, or the IP address, or the region, or whatever, so it's impossible to know what others see. The developer of a book-focused shopping site is likely to get very skewed results for a book related query. My results were noticeably better.
The author says that a Bookshop.org list they created that links back to Shepherd is ranking #2, and this kinda makes sense to me. Bookshop.org sells the books, it makes sense that would rank above a site that only links to (and makes money from) sites that sell books.
SEO, and people getting annoyed at not ranking, has been a thing for 25+ years, I don't think this instance is any different.