An ARC or Early Reviewer tag is the best solution to this in my opinion. Early reviews are an essential part of the launch process for authors, especially indies trying to build up word of mouth. Blocking early reviews entirely would discourage authors from embracing hardcover.

What about those of us who get ARCS and review them before the publish date, sometimes months in advance? Are we going to punished and blocked from adding a review?
I think what Goodreads have recently added is a good idea: if you want to add rating or a review of an unpublished book yet, you must add the book source. Whether it's a NetGalley of Bookfunnel or a publisher or Edelweiss (and maybe add your username? To make sure it's all transparent and honest).

For me, I feel like this is essential for any site that wishes to truly challenge Good Reads (noting the recent controversy). If people get an advanced copy, then perhaps they could post a review if they had some kind of verified status (possibly a membership tier in Pro) that would then be visible pre-release.

This one seems like it'd make sense, but there's a caveat - advanced reader copies. Those reads and reviews are before the book is ever released.

Maybe what we should do is hide reviews/ratings until the book is released, and only allow "ARC" reviews before a book is released. I think that would make a lot of sense.