I don't think you're coming from the same angle.
The person who isn't a low handicapper who gets a players iron is looking for clubs that will let him know whenever he makes a mistake, no matter what. This, for some people, helps them to get better faster.
Of course you can get better, and even to the level of a professional player with game improvement irons. It's a difference in how someone wants to do it, and what players irons do is force you to get better. Game improvement irons don't do that as much, so for the person who is basing their swing upon results won't necessarily know if he hits it a little off the sweet spot.
That's the idea, that with a players iron you know when you make a mistake and exactly how you made it, thereby improving your swing. They don't directly make you better, but they do require you to get better.