> The point of an insecticide is to kill the specific insect being a pest to the crop.

Even this can cause a collapse by removing a food source from other predators.

> I can save you the time. There will be no world.

This is true. Insects are food for a huge number of predators, and insect larvae are a really important component of having soil capable of growing plants.

Not to mention their role in pollination. 80% of plants are pollinated by animals, mostly insects. This includes 35% of food plants.