I had to ponder for a day. I read it in two sittings.

While all the characters were well-rounded, the main female, Greer, was not. Greer didn't grow, she was stagnant throughout the whole story and only reacted to plot changes, she didn't create them. Greer didn't move the story forward, all the other characters did. When life happened to them and when they made decisions to affect their lives, she was only a bystander that reacted. She did grow within the last twenty pages of the book but seemed like Wolitzer realized that the character was not interesting and quickly gave her a realistic HEA.

I guess, in a way, I relate to that, sometimes life is reactions, not creations.