If it is useful in expanding your comfort zone, it's useful, full stop. If it's useful in helping to get along with people who are different from you, it's useful, full stop.
If it's not useful to you, that does not mean it is not useful to anybody else.
1. We all have specific preferences in the way we construe our experiences, and these preferences underlie our interests, needs, values, and motivation
2. The MBTI is an accurate measure of #1
There's also an implicit claim that each of the 4 dichotomies are well represented by a binary value.
There are far more claims made about it by Meyers and Briggs, but those 3 are baked into the MBTI test.
People have definitely had their comfort zone expanded by following advice in horoscopes, but that doesn't mean there's nothing to "believe" with regards to horoscopes.
Horoscopes are useful to people otherwise inclined to get stuck in a rut. Likewise, the I Ching. You don't need to believe either one for it to be useful. Not believing is an intelligent response, but not everybody is so equipped. Intelligent people get stuck in ruts, too.
When I took the MBTI in secondary school, it was stressed that the specific point was to discover which of the 16 types you were, and that knowing which type you were would be helpful in life.
As ("even") Heinlein said, specialization is for insects.