After being into the story for about 2h I actually like the new gameplay. I honestly think they got the progression thing right this time, but need more playing time to verify. By now, the races on the world tracks are pretty easy with a car matching the points.
Regarding the AI difficulty:
I preordered and therefor got the two GT3 cars, and gave them a try at the Suzuka GT3 Cup race. I'm a B(+)-Player in Sport Mode but the AI gave me a real challenge keeping up with them. They are really quick out of the corners and I even noticed them defending the racing line approaching corners after the long straight, so in sum they are really fast and decent. I tried setting the difficulty to "normal" then, but almost couldn't feel a difference. Don't know if its just me having to get used to the physics again after not playing for quite some time...
Same is with the track experiences: If I remember correctly, this was no challenge at all on GT Sport, and I completed almost all sections on familiar tracks in gold on the first attempt. In GT7, I hardly got silver on the first sector in Suzuka and just got close to gold on brands hatch, which I (thought I) know quite well.
All in all, I really like the game, the gameplay and of course the graphics. To me, its like a breath of fresh air after GT Sport and I'm curious what they have in store for us in the future (updates, DLC, etc.) Of course I would have loved to give the new cars like the F8 or AMG Black Series a try immediately, but its ok that you need to be in a game for a certain amount of time to get there. Just like in open world titles, where your character is weak and the map is undiscovered in the beginning.