In Forza Horizon 1 when you completed a race in career mode that race was open to be raced again. So after a while there would be dozens of races available to try out with different cars, set ups etc.
But in Horizon 2 you cannot do this - the career is a bit restrictive. You have a choice OK, but can only do what’s next on the agenda. This in itself isn’t so bad, but you have to do another one of those irritating road trips to get to it and listen to that guy wittering away about stuff that you already know about.