Customers are not to blame, individually they may be strange, but in numbers they are always right.
To everyone it's own, if we believe that the car team is different from the core developers of S397 (UI and DX11), the GT3 pack mess is not ISI fault at all.
With four skins for each car (nice look alike of real skins, with no real sponsors, with a fantasy Croydon Endurance Series number plates), similar to what URD did for their EGT pack, you would have avoided many complaints, as well as balancing sounds (interior vs exteriors). When you know how easy it is to have skins painted by making a simple request to the fan base (participated in a GT mod version, we asked for skins and in a few days our problem was to sort and select all the marvelous skins sent to us for free).
To be honest ISI made some great cars (Stock Cars for instance) with three slightly different cars and their skins, and some great cars at their moment (ISI C6R GT2, FISI 2012, AC Cobra, DW12 second version, BT20, Historic F3, etc.). They were unable to bring graphics to the level of other games, and that is a fatal flaw on the gaming market since it exists.
Cheers.