Each golfer will have a point in their bag where ball striking starts to become a little too inconsistent.
As you go up the bag from the pitching wedge the shaft gets longer (in most sets) and the loft gets stronger.
A longer shaft and stronger loft will test your technique.

There will be clubs that you’re confident using; able to hit the green regularly with.
Then you find a limit. For higher handicaps, it might be as early as the #8 iron.
For mid-range handicaps, it might be the #6 iron.    

Which is the longest club you can use on approach shots with any degree of confidence?
Why not forget about handicap or scorecard, and set yourself a target to improve your technique
so that your number moves 2 clubs higher?