I don't agree with your statement, sure practice makes perfect but only with the perfect means.
Even a worldclass F1 driver wont be worldchampion in a lousy car or with a ****ty setup.LOL
Ask Michael Shumacher.
i have to agree with you, the setup makes a lot of difference, and we could see this in 2010 championship, when some car decided to stop developing the car, during practice they concentrated mostly in the setups of the car for that track while some teams that introduced new parts, have to study the parts and Analise them which cost them a lot a setup time and we could see that the difference between them were not so big, and that is why Hulkenberg got pole in Brasil and Kubica and petrov could hold Hamilton and Alonso.