To be more specific, Puustinen's problem is that he has no definable traits that suggests he should stick in the NHL. His best trait is his shot, where he can absolutely pick corners and has a lethal wrist shot when he gets it off. But the problem is that his release is so slow that NHL teams can clamp down on him before he has the ability to get off that shot. He has the space to use it in the AHL but that doesn't cut it in the NHL.
He's small, soft and not good defensively while also not being particularly fast and not having a quick enough release to be a good NHL goal scorer. What is even left there after that? He's another Emil Bemstrom type of player, good AHL producer but not a legitimate NHL guy.