The meaning of This song ... The reason they wrote it was to explain the concept of Jeremy Davis ( bass player ) leaving the band for personal reasons . So I guess the song does have to do with the importance of friendship .
Paramore is a great band, wehn I first heard of them, I completely underestimated them...Now, whenever I hear any of their music, like this song, I will stop whatever I'm doing to listen to this band do their thing... :)
I think it's about being friends or more than friends, but then they lose each other somehow, like through a fight that started over a misunderstanding or something. Hence "this isn't what you wanted."
But that's just me.