Generally (but with frequent exception), I believe coaches are made better to the extent they have both experience and success in what they’re instructing. For example, I would be hesitant — though not absolutely resistant — to take guitar lessons from somebody who couldn’t strum a simple G5 chord. Same with accepting financial advice from those deeply in debt, or nutrition advice from those struggling with obesity.
But as I said, there are exceptions. The obvious one: having and beating cancer doesn’t make you a qualified oncologist, etc. I also don’t believe a coach must be a world champion to coach world champions, nor do I believe a coach must be *as good today* as they were in their twenties or thirties. Additionally, it’s possible a coach who is overweight has still lost weight and learned much from that experience; which means our initial impression may be misleading. Same with someone who has reduced their debt but is still in debt: they may indeed have valuable insights to share on the basis of the progress they have made. Finally, just because a coach has an awesome physique, can lift a ton of weight, has 1m+ Instagram followers, is not by itself an endorsement that they are capable of transferring skills and knowledge consistently to their clientele. Personal success is different than coaching success. While one may assist the latter, it does not guarantee it.
Thus, one must look beyond the personal experience and successes of coaches/mentors/instructors/doctors, and to their progression track record. The question is have they been able to predictably and repeatedly generate results?