I noticed that in this game you can't setup the same level of AI for all cars and all races. To tell you the truth I am a little disappointed about PC2, the previous version was much better, of course is just my opinion, but project cars 2 it does not convince me too much.
I think PC1 had the same problem. Probably what was initially confusing was that you 70 rating in PC1 wasn't maybe a 50 rating in PC2. That makes you psychologically feel like a worse driver.
I can't agree with you about PC1 being better. It seems that PC2 is better in almost every conceivable way. I especially enjoy the manufacturers and invitational events.
Also, the Ai difficulty level problem has a lot to do with realism. In a real race, drivers have lap times that are pretty close to one another. If like me, you start out 7 or 8 seconds off the competitive lap time then it will be hard to set Ai that matches your speed.
What I do is practice in time trials until I'm competitive with the Ai. It takes a lot of work but it's very rewarding. I've had the best racing experienced in PC2. Races where I had to practice over the course of a few days before I was good enough to win. But winning was so rewarding.