you cant really say that reality is same for everyone, because there is also a subjective reality. subjective reality doesent mean an illusion. subjective reality is composed about the things in reality that you do know. the tricky part is that you cant always know if you live in illusion or not, but not knowing about something doesent make it less real.
you cant really say that mbti is an illusion imo. why? well mbti measures preferences, not strict traits. and you are typed by these preferences, if you wouldnt have these preferences, you wouldnt be that mbti type. if you think you are one type, but in reality you are another, that doesent make mbti an illusion either, it just means that you are under an illusion that you are some type that you really arent. and about functions. its clear that jungian functions arent different parts of your brains functioning, they are just names given to different types of brain usage. if you think otherwise, its still not the mbti that is an illusion, its you who lives in illusion where mbti is something that it actually isnt. it doesent mean what some profile says about entp, those profiles are just general descriptions about stereotypical entp. it doesent make any difference if some entp description said that every entp has autism, because in that case the profile would be incorrect and therefore not real. but if you believe that statement about entp, you are the one who is living in illusion about this.
you see there is not just one reality and one illusion. people might be in illusion that its allowed for everyone to own a gun anywhere in usa without any licenses. but the same person who lives in that illusion might know that obama is the president of usa. ofc everyone is in illusion about something in their lives(or everyone who has any sense about this world), but that doesent mean that they might not see the reality in other things.