Who is a review for?

Who is a book review meant for?
Who are MY book reviews meant to engage?
KB/KT Grant has an opinion:
Reviews can be cruel and for the author, heartbreaking. But reviews are not for the author. They are for readers. Authors, the reviews aren’t for you!
In my case, and in my opinion of my reviews, no, I disagree.
My reviews are mainly for the readers, to point them at the books, yes, and give them more information. Would they possibly like this book? Should they bother picking it up? Is this book for a reader like them?
My reviews are intended to be an engagement with the author as well. They aren’t meant as formal criticism, as deep essays on their work, but it is a communication. “Hey, Laura Anne Gilman. This is what I thought about your book. This is what I liked, what I didn’t think worked. What I took away from reading your work. I want an author to read my review of their work..
I understand many of the authors I read and review will never read the review I write and don’t want to. But it is there for them to read almost as much as the readers if they want to.