It really depends on your goals for the dog. What is a finished product in your eyes? There are a lot of great hunting dogs out there that have not been force fetched so based on that, I'd say no, you don't need ot FF your dog if you just want a reliable hunting dog who is steady, will retrieve mulitple marks and will do some basic handling. All of that can be accomplished without force. Non Force training programs that come to mind would be Wildrose or Milner. There may be others.
With that said, I want the best trained retriever possible and to me the best programs are the ones like Lardy's TRT (ad in upper right of page) which does include force fetch as the foundation for the rest of the training. If you choose to go this route, get some help from someone experienced or send the dog to a pro. You're right in thinking that you could "screw up a good thing" if it's not done properly.