What I see is no person is sane due to how life is. Life is hell and no person is perfect. They have at least one mental disorder no matter their MBTI type which everyone can have that disorder equally.
Psychology noobs believe MBTI is a big shot, people only use 4 particular functions in a particular order which they believe they should, there are only 8 functions, et cetera. In reality, neurotypical brains using Fi and Te functions regularly when they have to no matter their MBTI type because these functions are vital for survival (e.g. autistics are autistic because they can't use Fi and Te properly but they do have an evolved Ti function no neurotypical brain can use). So for example every neurotypical brain using Se function when they see a lion that going to attack them. Every neurotypical brain using Si function when they are in a reminiscent mood due to their loved one died. Et cetera et cetera.
It's a mistake to think everyone should only use particular 4 functions in particular orders. People use whatever functions they want depending on the situation therefore no one has one particular MBTI type. For example, a sad INFJ can go into Si + Fi mode in a way they may cry for the same memory by dwelling in it for a month while a vindictive INTP can plan so a perfect revenge plan with Ti + Ne + Te + Fi you may believe they evolved into an ENTJ
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Some think people are being unhealthy/mental when they use the functions that are outside of their function stack but it's not necessarily so. For example, an ESTJ can go full on Se mode when they see someone they fell in love while an INFJ can use Te to arrange a perfect birthday party for a friend by giving orders to people around and therefore seem like ESTJ.
Why people can use whatever functions they want is because of adaptation. Those who can't adapt will be eliminated by natural selection so don't try to limit yourself to one MBTI type.
There are a lot of wrong opinions on how people usually use their functions because they mistakenly thinking people only use a particular function stack while it's not necessarily so. For example, an ISFP kid using only Ti to think about a math question if the kid knows how to solve it. The ISFP kid doesn't even use Fi + Se + Ni + Te for it. The kid only using Ti because math is something you learn by using your Ti so once you learn the basics of math you can understand it so you use Ti to solve it. For example you likely to use Si - Ni - Ne - Ti - Te - Se - Fi in that order and other functions that are not known for MBTI If you don't know how to solve a math question regardless of your MBTI type because the task of your brain is trying to solve a math question.
In that regard, we came to a good point here. So, what function you use doesn't depend on your MBTI type. It depends on the task regardless of your personality because not every task is related to your personality, MBTI type, et cetera.
How you do the task depends on your personality though which where the MBTI type comes in alongside a lot of stuff like personality traits.
Everyone has their own preference for which functions they usually prefer to use in what order depending on their personality which is what MBTI is about. For example, an INFJ may say "I love you" to show their love while an INTJ may fix your sink to say "I love you". These are stereotypes though as much as how some people think a male is likely to be interested in cars while a female is likely to be interested in cooking. The thing is; depending on the situation, the mood of these people, even because of what they eat, etc. any people can do whatever regardless of their MBTI type so an INFJ may fix your sink to mean "I love you" while an INTJ can say "I love you" to let you know it. People's behavior doesn't only depend on their functions but it's what Carl Jung realized.
In that regard that's what Carl Jung tried to tell on how behaviors are affected by functions. He never meant it as functions are so related to personality and only particular personalities use particular functions nor people can be put into boxes like what MBTI states. MBTI is invented by some women, not Carl Jung and there was a good reason why Carl Jung didn't invent MBTI and whatnot type BS: Every personality is unique and you can't put people into boxes.
So for example I may prefer to use the same 4 functions in that particular order as other INFJs but not every INFJs likes Doritos as much as I do, they don't interested in lecturing people all day, they are not anarchist as me, et cetera.
Behavior doesn't only depend on your personality. It also depends on your functions (what Carl Jung realized), your past, your chemical balance, your mood, what you know, your IQ, your EQ, your active DNAs, et cetera. So not even the identical twins have the same personality and they don't behave in the same way. For example, some people get angry when they consumed too much salt even though they are normally a very peaceful person, some people completely change after they finish reading a book (I call this reality effect in which people's behavior changes depending on what kind of reality they live in). Et cetera Et cetera.
About personality disorders: Nothing in this reality is fundamentally good or bad. Everything that has a good aspect also has as bad aspect. That's why atoms are consist of positive and negative energies which without them atom can't exist. So a person has to have a personality disorder to even have a personality because every personality has its own negative aspect depending on your subjective opinion. The thing is, it's not a disorder for that person but it seems like a disorder to the others. For example, someone who has a serial killer personality loves killing people. They don't think something wrong with killing people because it's not who they are. Fundamentally nothing is wrong with everything, it's only wrong if you think so. So the serial killer actually thinks there is something wrong in your head if you ain't okay with killing a person. A serial killer will only think something is wrong with killing people if you kill their ego in which making them stop thinking it's okay to kill people will make them stop having a real personality. They will be a fake person and therefore their personality will die too if they dislike the way they being fake. For the very same reason, mental institutions are there for making people realize who they are and making them being useful members of society but they feel an entitlement to kill the personality if they don't obey. IMO killing a personality is the only crime I can't forgive and it should be punished by eternal life of extreme suffering because personality death is worst than literally dying.