Some bad experiences should not tarnish the entire methodology.
I wish like heck that in our company we had a true need for six sigma activities. It would mean that the 80-95% of problems that do not need six sigma methodologies to fix were already solved and the money spent on 2 black belts was not totally wasted. We would be so much better off.
Instead, at the direction of the corporate quality guru and the bobble-head nodding of our entire management team we wasted tons of money on 2 black belts that did their initial projects, which were widely ridiculed and a huge waste of time and money, and no more. And at the same time we often ignored using fundamental, basic quality tools and methodologies (like Ishikawa’s basic 7, PDCA, 5-whys, etc.) to attack the many problems that were allowed to continue to negatively affect us month in and month out and in many cases still affect us 4 years later. We had black belt projects going while having over a hundred open and past-due CARs. Now tell me that makes sense!
In a situation like that when anyone tells me we need six-sigma I know they are snake oil salesmen.