The reason these people say the cars are on rails, is because the played with the default setups. They are dailed in for INSANE amounts of understeer. Even with TC off it is very hard work to get the rear to slip.
But just try this: Turn TC off and set dampers fast & slow to 0, springs @ 1200/900, ARB @ 2000/200, front wing to +3 of rear wing. And then all of a sudden you spin if you floor the throttle. Just as it is supposed to be.
They just did not bother trying GP4 without the default setups, thats all. If you think that you know what a GPx product is, if you have not touched the setup screen, how much do you know about GPx or even F1 anyway?
It's only after we've lost everything, that we are free to do anything.