A Body Balance for Performance certified golf instructor is trained to do more than just tell you what to change in your swing. Body Balance assessments are used to "connect the dots" between swing patterns and physical strengths/weaknesses. If you keep making the same fixes, only to address the same issues later on, a Body Balance (or Titleist Performance Institute) trained instructor is a good choice.
Each of us, from a biomechanical perspective, has a different collection of tools in the tool bag. Any given swing model/method requires certain physical abilities to enable effective application of that technique. The issue is not one of overall fitness, but personal make up.
To get the general idea, go to
fit test and take the self test. You'll find some tests are relatively easy, some quite difficult, and all these variables can impact your golf swing.