Its not about the event or the car type. Its about the fundamental way the cars drive.
Have you played the previous games? The very first, on Xbox, was super evil hard... but an amazing rush when you hook it up. It has gotten progressively easier to drive with each new version, but the jump from 3 to 4 is absurd.
I had handful of top 50 times in Forza 3 and logged a couple hundred hours playing.
The general consensus is that the driving physics are better than ever. I have no idea what you are talking about.