Would like to have an optional alternative to the star ratings since I, personally speaking, don't really quantify my reading numerically but rather by how much I felt I enjoyed it.

Something like a binary rating system with at least three options (like/dislike/ambivalent) or the traffic light rating system which is similar to the former but uses colors instead (green = like, red = dislike, yellow = ambivalent).

Star ratings just leaves me trying to guess which number(s) best correlates to how I feel about a book which just ends up with me not rating them at all.