You make some good points.

I think the Race_1 sets, especially for the LX, RA and FZ cars should be much more balanced then they are. It would give a much better impression of those cars to drivers trying them for the first time. Also, I personally think the brakes are generally set too high and too far forward. The basic sets provided with the game should not be "on-the-edge" max hotlap speed types of sets, but 60 lap tire saving consistent types of sets. Once the player gets good and consitent laps out of these sets, then they can start tweaking to get the car more to their liking for speed. I personally really enjoy tweaking sets, but I like to have something close to start with.
As far as the sliding goes, well, lets just say it has been dicusssed a lot.
It does seem that with the cars that have a rear weight bias, that the slides are harder to catch than they should be. This could mostly be the result of us not being about to physically feel the back end kick out at the beginning. Or, it could mostly be poor setups. I think both definitely have an effect. It could be the physics are a tad off... almost like the tires tend to stay sliding once they start sliding instead of wanting to regain grip after they start sliding.
But I think the main point of your post was that the setups provided with the game should be improved for stability and to provide a good base for learning. I would have to agree with that.