His criticisms are extremely harsh, and feel biased to me. He interprets every scene that is remotely ambiguous in the harshest way imaginable.
That said, the book is a failure, but it's not because Riri is an inherently failed character. Rather, it's because they utterly refuse to tie anyone to the railroad tracks.
It's impossible to care whether Riri wins or loses, because she is never trying to protect anyone. She just sort of gets into fights randomly. So it never feels like there are any stakes. It's like, if Riri loses, then what? Then nothing in particular. This book desperately needs Riri standing between a villain and a little pigtailed girl holding a puppy or something, and it never happens.