We have one-design world championships every year, and every four year the best sailor in each country races in one-design boats for Olympic Gold.
America's Cup sailors have excelled in both, Dennis Conner is the only sailor in history to win the Star Worlds with five bullets and Russel Coutts won Gold in the Finn class in 1984 in LA. There are many others...
First and foremost, the America's Cup is intended to be a design and development contest. The best sailors in the world won't win the America's Cup in a slow boat. If the design team delivers the second best group of sailors can win the cup and there is nothing the "better" sailors on the other boat can do about it no matter how talented they are.