Yeah the way it's all put together is interesting and fits together nicely within the framework of itself, but it doesn't mean that it's science. When it moves past just being a theory removed from practical application, it fails. Yes, I relate to the ENTP type. Yes, I do see a lot of truth to it in a lot of instances in my life. And you may, too. But that doesn't make it true. All it does is make it true based on our perception of it (which is limited). I'd love to see psychologists prove it! I quite enjoy MBTI and Jungian function theory. I enjoy seeing how it might align with certain aspects of my life. But just cause I enjoy it, doesn't make it universally true. It doesn't make other theories that are better, not as good.
Blah blah blah, anyway, if some theory comes along that is cleaner than the old theory (and still addresses the same topic) then it wouldn't necessarily discredit the old theory, but the new theory would be put into the system more towards the "right" end ahead of the old one, thus sliding the old one back. "Good theories" (in theory) are ones that explain everything with no additions (ie. excuses), with no submissions (ie. it works for x amount of the public, but not for y amount) and is based on sound logic that agrees with observation.
I may have any number hair-brained ideas that are logical and seem COOL, but it doesn't make em universally true. I can believe it, but if something comes along that explains the same thing better (ie. meets the above criteria) then the old theory's gets pushed further towards "wrong."