One is to shoot to a script, like I would for a more information based subject. The other is more common if you have the time and money for editing. That is to get an outline of what you want to do, shoot the whole process and then make the film in post production. The first is like building a brick wall, the other is like making a sculpture. Both have their place, but most people choose the second way and end up in the most mess.
Pre planning can never go wasted.
Too many inexperienced people go into a production without a clear idea of what they want and end up with spaghetti. The funding process is a chook raffle and there are too many people going for too few broadcast slots. Only people with a fairly high profile and good networkers are working continually. There is a dumbing down and a demand for high rating programs like sport and celebrity driven material. The culture will change, but when and to what, is anyone's guess.