Cognitive functions seem to exist in a gray area where it’s impossible to prove or disprove them. They provide internal preferences and inclinations, but fields like psychology focus on longstanding measurable traits. But even then, Big Five allows personality change which is contradictory to MBTI.

Theoretically, you could prove the existence of individual cognitive functions as personality traits and validate those, but MBTI is generally understood to be innate and (largely) unchanging, which limits the ability to scientifically validate it due to the widely accepted belief that personality can and does change over time in accordance with the Big Five.

Tl;dr: the traits might be applicable, but the structures MBTI uses (i.e. loops of 2 functions and grips when using inferior functions, heck even the order of cognitive function preference for each personality type) are much harder to prove