Good point. I'd be horrible for TKD. I am good with kicks, but have an inherent dislike of higher kicks PLUS some apparently genetic inflexibility in my hips. Bad art for me, but it seems to agree with my brother.I believe there is another factor, and that is how well a person is "cut out for" a particular system or methodology. For some people a particular system is simply a poor match and they will never get any good at it, no matter how good others are with it, or they simply dislike the training methods or the approach to combat and so will not stick with the training and instead will find their interest in a different method.
This issue alone negates all of the arguments over XYZ style is the "best". There is no objective way to make such a claim and if the "best" system is a poor match for someone, then it is the worst system.