No one is saying MBTI is a failure. Instead, you can say MBTI is limited in what it can measure and tell us. This is regardless of whether you subscribe to a 4 letter model or a function model. This is what is trying to be said. It’s obvious, and everyone will agree to some extent (probably somewhere between “MBTI doesn’t explain the laws of physics” and “MBTI doesn’t explain ambiversion”). So yes, OP is pointing outside the system - but not very far outside. That’s a limitation they’re trying to point out.
The functions are a useful shorthand we can use to describe various ways of judging and taking in information. They aren’t physical properties that you have or don’t have. They aren’t reality. They are part of abstract system that tries to have a practical purpose. If you define the system as allowing only 1 feeling function (E or I) and apply that system to how you interpret everything of course you’ll only see that. If you make a system that allows for both Fi/Fe and start applying that it will be different. Nothing about reality changes.
It seems the debate is about how closely MBTI maps reality. The function model provides a lot more detail than relying on 4 dichotomies, but it still doesn’t fill in all the gaps. If this world map is the 4 letter model and this one is the function model, the second map is way better. It’s more useful, it has more detail, it’s more complete - but there’s still problems when you compare it to the Earth. That’s the point.
Along with that, there are so many versions of MBTI floating around. The way Celebrity Types and the actual Meyers Briggs Foundation use it is completely different. Jung’s writings are way different. Socionics is different. Keirsey is different. Depending on the purpose, any of of the above could be very useful.
You can say 'what about people with both Fi and Fe?' but that's like saying 'what about people with both 5 fingers and 6 fingers?'.
It’s like that trick question: “How many months have 28 days?”
Socionics gets around splitting functions into E/I by modeling all 8 functions. So if we base our own model off of Socionics it’s very easy to find someone with both Fi/Fe.
At the end of the day, the best thing to take from OP is that there’s a lot of information out there. You may not agree with all of it, it may not all be true, but it seems silly to be so dogmatic about one specific model of personality, to the point where it impacts everything we post here. It's not backed by science, people who are professionals disagree about it and people who are hobbyists disagree (obviously, hahaha). I think it’s good for everyone to have a decent understanding of functions so we're on the same page but not if we’re so pedantic about talking about them that we overlook other things being said.
