All three are essentially just short book reviews written by experts on the topic, for example, a book on the history of Constantinople written by a Greek history professor. The books reviewed are definitely more “serious” and sometimes a little niche, so you usually won’t see the stuff on Amazon top charts.

In any case I highly recommend it, if only as a way to discover some new books and learn about different topics:

https://www.the-tls.com/ https://www.nybooks.com/ https://www.lrb.co.uk/

Yes, the caliber of reader reviews on Goodreads is all over the map. But it is huge, passionate forum for active readers of all stripes. Spend a little time with lists, filters, reading circles, etc. -- and you can semi-reliably get both reviews and recommendations that are well worth the time invested. Most major publishing houses know this, accept it, and have even come to appreciate it.

As a hardcover author in 2017, I found that my publisher's marketing/publicity team was very comfortable with Goodreads' prominence and felt that its review-by-review quirks balanced out over time in a way that ultimately was quite good for promoting wider readership of interesting books.

I don't quite see why the author shuns them.

It seems that when given the option, folks don't choose traditional media for curated books-to-read lists or literary criticism.

Just like they are tending toward social media for news and streaming companies for tv and movies.