Hi Jammy,
You're right, kart driving in GTS got completely different compared to the previous editions. Some like it, some hate it.
The most important change is the so called DOR (degrees of rotation), way way less steering input is now needed to make the kart turn.
In addition to that, the physics have also changed. More off-throttle understeer, more on-throttle oversteer.
Along with the way lower DOR, the right amount of throttle input is now crucial for fast cornering but also to avoid to go whide (understeer) or/and to spin (oversteer).
All these changes at ones makes karting on GTS a pretty challenging game.
But let's go back to DOR real quick. On GT5 and GT6 the difference in DOR between cars (in a general way) and karts, was already obvious, some adaptation time was needed when switching between them. This difference got way bigger now, which increases the need to get used to the changes in DOR considerable.
In my particular case, and having already done over 9000km (~5600 miles) with my kart in about 5 months, coming back to karts from some hours practicing in cars, I need about 30 minutes of non-stop lapping to get close to my normal pace in karts. Not even to mention how many times I crash or spin within these 30 minutes
As I've already mentioned in this thread, the best way to get used to karts is to drive exclusively these little beasts for a long time while avoiding to drive any kind of car for the same amount of time.