The fact that the red team won this match...

The most definitive response to the "plot" criticisms regarding Rin is undoubtedly the result of this match. Right now, it's incredibly difficult to name a quartet that could beat a team consisting of Isagi, Barou, Nagi, and Chigiri. Despite that, the fact that the red team won proves just how much Barou, Nagi, Chigiri, and Isagi have developed within the story in such a short time. Rin has always been like this from the very beginning. Not being able to accept this even after 300 chapters is not a valid reason for "plot" criticism.