That's the best they could do. I doubt that PD, even with more sound engineers would be able to sample all the car sounds before GT7's release. Provided that cars sound somewhat like their real life counterparts, and are not miles out, I'll be more than happy.
One car that really needs its sound replacing is the Audi Sport Quattro S1 Rally Car. It sounds uncharacteristically weak.... There's the Audi R8 GT3 car that sounds exactly like the rally car. They should take that sound and transfer it over to the rally car. Job done!
The R8 GT3 car in GT6
The Quattro Rally Car (Sounds similar doesn't it?) I can only assume that engines in both cars are similar in design (someone who's familiar with Audi engines please tell me this is so
)