In my experience most management concepts are applied poorly. Many of the concepts may also be bad. For example, performance appraisals are both done poorly and a bad idea. The solution is not to do performance appraisal righter: for what to do read Peter Scholtes.
But, many tools and concepts that are applied with poor results, where the actual application is criticized (with good reason), can be used successfully. I would put benchmarking and time and motion studies in that category. Most of the time they are done poorly and produce bad results. But they can be done well, and provide value, so long as you have the right management system surrounding it and execute well. In practice I think, one thing that helps separate good managers from bad ones, is knowing how your organization will actually execute (not just dreaming about how nice things could be if only…) and not just trying things that they should know will produce bad results in their organization.
Based on my comment on: Time & Motion Studies Are Not “Discredited,” Just How They Are Used