We learned from Six Sigma failures. Let me share an experience at a previous employer.
After some success in the Quality arena, a Six Sigma program slowly disappeared. Why? It solely focused on DMAIC projects that took 6-12 months to complete and were too methodical.  It was too focused on complex statistical analysis. It was harder to apply these tools in operations, supply chain, or where data availability was a challenge.  Yes, some Black Belts were successful and embraced their nerdy side, but they failed to engage with the employees who don’t speak statistics. It also built a culture of superheroes... “Let the Black Belt come and solve this problem”. A handful of employees got rewarded by solving big problems instead of not allowing problems to grow in the first place. And they didn't focus on sustainment. Â
After top leadership recognized the need for simpler tools to engage the workforce, the opposite effect took place. A transition to Lean alienated previous Six Sigma resources who saw their efforts getting "replaced". The two training programs were never integrated. Six Sigma resources moved on, their expertise was lost.
At Belt Course we've integrated Lean and Six Sigma into the Operating System of our clients.