That certainly used to be the case. But like Bob Dylan said, “The times, they are a-changin’”. Composite materials are lighter than steel and therefore represented the best option to build lighter, more flexible shafts. To date, plenty of golfers can benefit from iron shafts that weigh less than 60 grams and that’s still the primary use case for graphite iron shafts.   Golfers with slower swing speeds can benefit from lighter shafts than help them swing faster which creates higher launch, more ball speed, and ultimately more distance. But, because graphite shafts only served the needs of a particular set of golfers, it got a reputation. And that history is a good bit of why better/faster golfers often carry a stigma against graphite iron shafts.   But that history, is well, history. Fujikura, Mitsubishi, Aerotech Steelfiber and LA Golf are several manufactures that produce graphite iron shafts that are played around the world by some of the strongest, fastest players in the game (See: Bryson DeChambeau)   So, no. Graphite isn’t only for slower swing speed players. The options aren’t as plentiful as steel, particularly in heavier weights (120gr+) but that’s slowly changing as well