That's like saying read the bible, it has all the answers and is crystal clear. That is why we have unlimited versions of christianity, each of whom is convinced they are right. That is also why Agile people seem to claim failures as "you just didn't do it right". My problem with Agile is that it claims to be all things to all people mostly by being completely unspecific. This allows the bad business processes to be propagated because Agile will equally say do design if you need it, don't do design if you don't need. If you have been failing in a process, then any process change could help. I think Agile has been successful "rescuing" people who were failing. Since their is no head to head comparison, there is no way to really now what made it successful. I think there are many cases where Agile is a very poor fit. And I have personal experience with switching from a working process to Agile where it decreased output, productivity and quality. That being said, trying to do a full end to end design up front is a bad idea. Doing little or nothing, for any system beyond the most simple, is a really bad and expensive idea. Unfortunately, this is how Agile is often interpreted.