bookworm, I may have oversimplified, but that is what instructors do!
What I meant was:
The lift and drag forces on a body can be found by integrating the pressure times the area around the body if the pressure is known. The pressure can be determined from Bernoulli's equation as long as none of the assumptions of the equation are violated and the velocity variation is known. How is the velocity variation determined? A simple one dimensional, Venturi flow relation could be used. But this gives the wrong answer since a wing section isn't really half a Venturi nozzle. A similar incorrect answer is obtained if the velocity is set to the velocity necessary for air molecules to separate at the leading edge and meet at the trailing edge of the airfoil. The best way to get the velocity variation is to use the "Newton" theory and determine the flow turning caused by a given shape. It isn't easy to determine the velocity variation for a general shape. But for some simple shapes, the velocity variation can be determined. In order to use the "Bernoulli" theory to solve a practical problem, we usually use the "Newton" theory to determine the velocity distribution. (emphasis mine)