Myers-Briggs is the single most useful mental model for personality types in existence, or that I know of at least (especially the modern versions like 16personalities.com).

I've heard a common complaint that "traits are a spectrum, not discrete categories." But often in biology, this is not exactly true, just like there are light brown leopards and black leopards but no dark brown leopards.

Don't "listen to the scientists" who say otherwise, those hopeless reductionists who obsess over what is true but useless rather than what is faulty but useful. Pareto said it right: "Give me the fruitful error any time, full of seeds, bursting with its own corrections. You can keep your sterile truth for yourself."

Of course it doesn't cover everyone well or every aspect; it's just one model of many, but it's useful and predictive.

As for zodiac signs...I can see some correlations popping out based on whether you're young for your grade or old for your grade (like Malcolm Gladwell talks about in Outliers), or perhaps when your parents decided to "mate" says something about them which says something about you, but yeah idk how deep it goes.