Do you mean that trying to type ourselves by cognitive functions limits out individuality and hinders our insight into our own mental processes and therefore hinders our cognitive capacity in the process? I agree that we can probably use any of the 8 functions and jingoism theory is a bit strict, but the theory is only a guideline, we shouldn't feel the need to operate or limit ourselves to the box but use it to help us see our general proclivities and whatnot.
If that's not what you mean then the title is not self-explanatory where I am concerned. Even if it is, it could have been made clearer but I understand English is not your first language...this one may have been lost in translation.
I don't know what the OP meant, but I think they hinder clear thinking by introducing too much jargon: even Myers-Briggs test letters don't have clear or self-evident meaning, but cognitive functions are even more difficult to make sense of. Second, they represent skills that at one point or another every well-rounded person must use. Given that they are eight then there are many possible ways in which a person might develop some and not others. Finally, in my experience with supposed tests of them, they never appear in the order in which Jung or other psychologists suppose they should, which maybe is a problem with the nature of unverified internet tests, but sometimes the tests come with very weird results in light of Jung.