I think I'm annoyed with how it has created R&R mechanics that can't diagnose their way out of a wet paper bag. They read codes and Remove and Replace (R&R) blindly. They continue to that until the car is working again. The customer pays for all the good parts replaced until the problem is fixed.

If there were only a way that they ONLY get paid for replacing the part that caused the problem in the first place. That would incentivize mechanics to actually properly diagnose cars.