Just because he was doping before the CA and after doesn't mean that his results would be the same. His doping program clearly became more systematic and more refined. There is probably little doubt that his overall training and diet changed after the CA as well. He became totally focused and controlling about everything. Exercise, wind-tunnel training, diet, and doping. It all works together. He clearly changed many things in his life after the CA diagnosis and treatment.
However just because everyone is doping doesn't mean there is a level playing field. Some doping programs work better then others. There is little doubt that Lance had an "unlevel" doping playing field. It was probably more refined, better researched, better funded and more controlled. There is also little doubt that during his cancer treatment he gained alot of insight in the medical world and how to approach doping more systematically. I am sured he picked the brains of many medical personnel and many people form the pharmaceutical industry.
All doping is not equal. Some will kill you, some will do nothing, especially if you are not dosing appropriately and not using a tiered approach that builds to a goal with the treatments, and some will give very good bang for the buck.
The myth that because others doped, that there was a level playing field, is just that, a myth.