A core tenet of Lean manufacturing principles is the optimization of processes over people. Rather than blaming employees for any shortcomings, Lean's focus is to build quality directly into each and every process, thus enabling employees to be as productive as possible with fewer points of failure.
There are two key points to understand why focusing on the process will always trump focusing on the individual in the workplace:
1. Processes are the most reliable targets for improvement
Unlike people, manufacturing processes are by definition consistent and measurable. This makes them the perfect target to continuously analyze and incrementally improve! If defects are occurring, Lean teaches us that systems and processes are likely the root cause in the majority of cases.
It gives us the perspective to approach each production issue as an improvement opportunity, and that updating the process will make our jobs that much easier tomorrow!
Carefully adjusting and reviewing these processes eliminates weakness that could result in human error down the line. That's why Lean practices leverage systems like 5S, mapping value streams, standardized work, and Poka-Yoke (mistake-proofing a process). These systems center attention on the process, not on figuring out "who screwed up this time?".
2. Employee Potential is Limitless with Great Processes
When processes are bloated with excessive waste, variability, and bottlenecks, no operator--regardless of skill level--can perform at their peak. Cumbersome process tend to overwhelm people. By taking this burden off the employee via improvements to systems and processes, Lean enables everyone to take on more value-adding work that can show off their own employee genius.
When processes run smoothly and waste-free, employees are enabled to express their dedication to productivity and quality. You'll find employees have so much more to offer when your processes become robust enablers rather than a hindering obstacle.
Ultimately, when the primary focus is zeroed in on improving the process rather than an employee's mistake, better results are sure to come. Perfectly optimized processes can unlock higher levels of reliability and employee performance that focusing on employee weaknesses would never be able to foster in the workplace.
TL;DR - focus on improving the process over the person, and reliably great outcomes will follow!