To give one example of what?To give one example. Why sail a 49er when you have a job and maybe a family when you are going to get whipped by a small group of sailors paid to sail. Your 200-500 hours a year sailing versus there 2000 hours sailing or in the gym just won't cut it.
If your objective is to win in a class with minimum input, there are always going to be classes that are easier to win than others and it isn't so hard to figure out which they are. Olympic classes will be hard to win but there are others.