I don't like PDs custom tracks. I find them too wide, too banked, too hilly, and too simple. The exception is the kart tracks, but those are too narrow for side-by-side racing.
The custom track maker leaves MUCH to be desired but it is capable of producing decent race tracks. With some effort you can make tracks that feel realistic and provide a challenge to drive. NASCAR tracks have wide high-banked curves. Road courses don't.
At the risk of being immodest... Here is an example of the kind of track they should make for the seasonals: