I wish it was hard to screw up. In fact it's very easy. If anything, the over-reliance on CNC and multi-turn machines has driven the quality of certain parts into the ground. If it was 'easy', our reject rate wouldn't be 80% and we wouldn't need 100% inspection just to keep our assemblers busy stocking orders.
There's a major difference in quality from PSA up to Colt and onto the boutique builders above that.