It’s a tool and nothing else.
It’s meant to be descriptive, NOT prescriptive.
In other words, if you want to wear your necktie straight and classy, then a mirror can help you to make sure that your necktie looks straight and classy. It gives you an accurate visual description of your appearance.
On the other hand, your mirror is not qualified to recommend to you how you should wear your tie, or what color ties you want to wear. Your mirror should not be prescribing your fashion for you. Those are choices for you to make.
These personality tests and systems are just tools for recognizing potentially useful details about yourself. If you like pizza, and a test tells you that you hate pizza, f**k the test.
But if a test tells you that you may like pizza, and you’ve never tried pizza before; well, add it to the list of things to try, because who knows, you might like it. The final choice is yours.
Sometimes these systems can help you to get some insight about your thought process, your creative process, and so on. But they’re all generic. MBTI has 16 types. Enneagram has 9 types (with 18 to 54 subtypes). The world, on the other hand, has 8 billion people.
These little tests are not going to be able to describe all of the specific details about you.
If you approach them with balance, though; they can be very useful.
Eventually, you transcend your own little narrow identity, and start getting interested in what the entire system can tell you about human beings in general. And then it gets even more useful. (Though the same limitations already mentioned apply.)