Greedy agile, waterfall and local minima

Everyone in the agile world can't contain their words about waterfall inadaptation to real world software projects. I have to admit, I am a fan of XP, scrum and most of agile approaches in general but I feel that people are loosing the big picture provided by the waterfall framework. Agile is kind of a greedy approach that lead you to local minimum where you are stuck too often. I would like to see someone creating value and velocity cost trade off of short term decisions. Those decisions are ofter push through agile methodology without questioning. Currently, at pivotalpayments, we are stuck in a huge local minimum created by such an approach and it will take such an effort to get out of it. The velocity created by a design choice taken long time ago was emazing at firt but it is slowing us doing now so much now. A major refactoring is required and we will stop development for some iterations. At least Agile adapts and give you the illusion of the optimal path...but everyone should know that the greedy approach isn't the optimal one and that looking at your feet won't help much going to your destination.