As I understood it, James Middleton does accept that he is in a privileged position and is thankful for it. I guess that the supporters were not only his parents but Uncle Gary as well. But even if you get the basics and a good financing, it still takes hard work to be successful. Okay, there are sons and daughters who become Crown Prince/Princess in Daddy's company, but even they have to work hard and show positive prospects or it's better for their inheritance to appoint a professional as head of the company.
And I believe what James did is creating a company who thrives on creative ideas. Okay, being the B-i-law of William helps but if the cakes do not taste good, then that PR is for naught.
So IMHO he does a good job (I haven't yet tasted his cakes) and time will tell just how much quality he offers...