The sales funnel (a.k.a. purchase funnel) is a method that envisions leads learning little by little about their problems and how your brand can help solve them, gaining knowledge until they decide to buy a product.
When you read it like that, you can see the flaws in this method. The buying process is convoluted and full of ups and downs, obstacles, and anything else that distracts leads from solving their problems. Also, it simplifies the learning process as one with a start and finish, whereas learning patterns tend to be more of an unexpected rollercoaster.
This begs the question: should the sales funnel be killed off?