I don't think Fed is a great player because he has a 1Hbh, and I don't think Fed is a great player despite having a 1Hbh.
When Fed was first emerging, people were already saying he might have the best one hander in the game. People talked glowingly about his backhand. It might break down against Nadal on clay, but what other player have you seen consistently exploit his so called weak backhand? Just saying, it can't keep up with the best left handed forehand in tennis history, and probably one of the top 5 best forehands in tennis history PERIOD, on clay, but his backhand is still one of the best strokes in tennis.