You could have the perfect launch angle and spin rate for your swing speed and strike the ball with the ideal attack angle, but if your lie angle is out, you’re going to struggle with accuracy.
For a straight trajectory with your irons, you need to square the club face at impact. And it’s a lot easier to do this if your lie angle is correct. When it’s too upright, the club face is more likely to close at impact and pull/hook your shot. When it’s too flat, the club face is more likely to open at impact and push/slice your shot.
There is no standard for lie angle in golf club manufacturing. Brand A’s ‘standard’ lie angle isn’t the same as brand B’s ‘standard’ lie angle. That means getting your new clubs fitted has to be the standard. Book a fitting now!