I'm not disagreeing with you. I definitely agree that using less (ideally no) pesticides is the best. But moving from a pesticide with more side effects to one with less is an improvement any way you look at it. Also, I believe it's an open question whether we would be able to feed the world population without using pesticides. If you have to choose between adverse affects on soil quality and potentially having people starve, the choice for policy makers is obvious.
Step 1: devise a sustainable system of growing food, where "sustainable" means that the process can be maintained for at least five hundred years without exhausting resources.
An example of unsustainable agriculture is a model based on mining phosphate.
An example of sustainable agriculture is a model where human waste can be converted into fertilisers (e.g. by processing sewage using reed beds, then charring the reeds to use as biochar and mulch).
Turn our attention to plants which will efficiently store phosphorous in a biologically available form, and ensure that the phosphorous we currently discard in effluent can be captured.
Treat spaceship Earth as a closed system and relise that we have to plumb our outputs back into our inputs or there will be a heck of a mess to clean up later.
There is also the issue of the begged question when asking, "how do we feed 9 billion people?"
