My opinion is, there isn't anything wrong with the racing aspect/championship setup of forza 4, except two things.
1. The hidden lobby points system makes it difficult to keep a points tally
2. The fact that you're expected or forced to have xbl gold to set up what you're looking for (this one doesn't bother me)
It's really easy to set up qualifying and practice sessions when you know how. I regularly set up SuperGT 30+min races against the AI. The only downsides for me are there are only two tracks from the last/current seasons and the AI is slow (even at their fastest options) unless you manipulate the settings to give them an advantage. i.e reduce your power or grip multipliers.
As I said, if you don't have xbl then the true racing experience of fm4 is somewhat limited, even as a solo player. I suspect this is down to Microsoft rather than T10