Doesn't sound like such a big deal for the average amateur, who has a pretty inconsistent swing anyway.
If you have 20 minutes you can see what it will do, and yes it is a big difference. It just only seems trivial to someone that has no idea what it does.
Here is what you do. I don't know what metal your cast irons are made of. But if a magnet will stick to the face of your club this will be easy for you. If not then you'll have to do a little more work. Maybe 2 minutes more of it.
Get your magnet and glue a fireplace match to the center of it with a glue gun. You have to have it 'straight', nothing else will do.
Once you have this done, put the magnet in the center of the face of your club.
Hold the heel and toe in your two hands/fingertips while you are facing the face of the club. Be certain the grip is in a position that seems correct as well. I do this standing up and holding the club, and you could too once you understand what you're doing.
Look at the point where the sole touches the table top or counter top and get it to a point where it is dead center of the sole.
Look at where the fireplace match is pointing.
Now slowly roll the club towards the toe and watch the direction of the match.
Now roll it back to the heel and watch the direction of the match.
You'll see, or you should see if you did it right, the match will point to the right when the toe is down and to the left when the heel is down. This is for a right handed golfer.
2 degrees at impact calculated over 200 to 250 yards can be 40 yards to the right with ease. Put some side spin on it and you've got a banana ball. You're in the trees.
There really is a difference.
If you can't use a magnet get a twist off coke top and glue the fireplace match to the center of it as noted above and then carefully tape it to your club face.
It'll give you the same variance.
FORE! Play Golf
The lie on my irons was 3 degrees too upright (+1 from OEM specs) and I was hitting ball on the toe ... consistently.
After flattening the lie angle and moving away from the ball (yes, moving away), I was hitting the ball in the middle of the face.
Yes, it makes a difference.