*nod* in a way, I think agile, as an actual methodology, has not failed at all, but instead has been integrated into the toolbag of any competent project manager (or ad-hoc equivalent). What has failed is the hyped up "A"gile method, which, like any hype, over promised on its universalness as a replacement for everything.
Sometimes I wonder if tech people are just inherently excitable. So much of our culture and identity is linked to loving what we do and related topics, it would not surprise me if we are unusually (but not uniquely) susceptible to irrational exuberance.