Even in math it’s possible to have conjectures that are likely true but may never be proved.
https://en.wikipedia.org/wiki/Goldbach%27s_conjecture
https://en.wikipedia.org/wiki/G%C3%B6del%27s_incompleteness_...
Even in physics, you have statistical truths like second law of thermodynamics. they allow you to generalize where precise computation is impossible.
So Jung’s insights into personality attitudes, dichotomies of perception and judgment seem like interesting conjectures worth knowing about, possibly difficult to prove.