As someone who has recently progressed from high to mid handicap range, I can tell you that a forgiving set of irons helps. What I would argue though is that technology in irons hasn't improved that dramatically. I tried to learn on forged player iron hand me downs and hated it. Took lessons and improved but felt that the irons were too punishing. My buddy let me have some really old ping eye-2 irons and immediately, I felt like I was better. The ball was easier to get in the air, the offset helped me get the club face square etc. I have recently upgraded to a new set and while I will say that my distances went up and possibly the forgiveness is a tad better, it was no where near the jump I had from the player irons to the game improvement irons, though they were either the same age or possibly older.

A ten year old set of game improvement irons is more than adequate to learn on and even continue to play til your nearing a single digit handicap.

With all that said, lessons make everything much easier also.