At the end of the day every car can be improved but nobody can make the car just for YOU, because everyone drives differently. I should know, I ran the biggest tuning garage in GT4 for three years and then wound it down and quit after GT6 as most people couldn't tell quality from quantity.
It would be beneficial for everyone struggling with setups to sit down, take a car, and drive it for an hour while not changing anything yet - and put some actual thought to how physics are affecting it under different situations. What happens at the front suspension when you brake? What happens at the tyre contact patch when you turn in? What happens when you begin to accelerate? And repeat the same for the rear. Not trying to be particularly fast, just thinking about the mechanical side of things and trying to visualize what's going on in the car.
After doing that, put more thought into how the settings affect the behaviour in each of those situations while changing one setting at a time for another hour. I can just about guarantee that those two hours would give a better result than using others' tunes for years.
