In other words, you don't understand it either. That is not surprising: you would need to learn something. That would involve work, so is understandably unpopular.
You mention that hucksters peddle it for things that it's isn't useful for, but in what context is it useful? The realization that people have different ways of thinking, abilities and interest, which in turn means they are good at different kinds of work isn't the invention of the MBTI. Why does a 4-axis test help with this? Why should people take it seriously, especially considering it's highly commercialized?
Anyways, you're just missing my point. You just don't get what my point is for. You don't understand it either.