Stupid
Problem is the results change with your state of mind. Which makes sense, since you don't always behave the same way
Yes
Predictive of what tho
It does not have any predictive power. And it shouldn't have. Mbti is helpful in understanding how you might adjust your style and how different could be work preferences of your colleagues. Anything more than that is unwarranted. It won't tell you who will be successful in what kind of roles.
Myers Briggs makes a lot of money. It was made by some housewife who was into Carl Jung. https://www.washingtonpost.com/national/on-leadership/myers-briggs-does-it-pay-to-know-your-type/2012/12/14/eaed51ae-3fcc-11e2-bca3-aadc9b7e29c5_story.html?noredirect=on&utm_term=.47fe8aa0c5e1
Was it ever bunked?
No, but it's been superceded by the Big Five personality traits.
Yes
Like.... ages ago?