I have been fascinated by the MBTI since the '80's. I'm an INXP, which is a combination of INTP and INFP. I was a passionate JW, as INFP's are about whatever they believe in. The "truth" was presented to me (as a child) in a way that I considered scholarly; i.e., there were lots of quotations from "authorities" to back up their claims, so the INTP part was drawn in.
The ESFJ type is "the salesman," so cults find them very useful. They are also upholders of institutions and tradition (as are all SJ's/guardians).
What I learned from researching the different types are (1) that I don't have to be so melancholy and serious and (2) to figure out which type(s) a person is after I've known them a while. It helps me to speak to them in a way that they can relate to. INFP's have a mission to help everyone to be their authentic selves.
The 4 temperaments each have 4 types:
SJ: "Guardian" - keeps institutions and traditions alive, resists change, is methodical, does things step-by-step, expects others to conform to his/her values and expectations, make good administrators, are usually the boss.
SP: "Artisan" - Free spirited and fun-loving, live entirely in the moment, become great athletes, artists and musicians because if they love to do something, they do it for long stretches.
NT: "Rational" - thinkers, tinkerers, want to figure out how things work, make great inventors, analysts, scientists, often full of self-doubt.
NF: "Idealist" - People who care about others, make decisions based on values and how others will be affected; NF's were at the forefront of the Civil Rights movement and the Women's movement, work to make the world a better place, not bound by tradition.