If there is anything we have learnt since the Enlightenment it's that we are prone to illusion.
The scientific method enables us to distinguish between illusion and reality.
And mbti is tailor made for illusion.
And I must say I have nothing against illusion providing it is seen as art or religion.
I do object when illusion claims to be reality.
A lot of assumptions about what something claims to be. But I also respect and follow the scientific method, however even within the scientific community there are divisions and disagreements.
Most of all the scientific method has it's own flaws and biases and following it as a blind religion is also dangerous. There are many entrenched ideas within science that could do with being un-entrenched. For example in astronomy there is a divide between the mathematicians and the engineers. The complicated mathematics used to measure and compare state of the universe are increasingly unproven with empirical methodology and assumption often rules true instead.
Faith in the truth of science can be as big of an illusion as any religion, even though I myself am not religious. Instead a critical mind should be used to examine all evidence presented and see where it stems from. A statistic can be falsified, a measurement poorly adjusted.
As for illusion and reality. I hold that all reality is an illusion of some kind, the illusion that what we see is real, when it is only a collective hunch of the senses and when I say senses I don't mean anything to do with MBTI.
Then we also each hold our own illusions inside our heads, as i'm sure you know well, these are the imprints we make on the world around us based on our own assumptions, biases and desires and as we imprint so are we imprinted upon.
MBTI is just a tool, a creation of our intent, it speaks of a desire to try and understand the deeper cogitations of the human psyche, the key to this is of course in the brain, but even now it is so complex that many of it's workings remain misunderstood or hidden from us. Also there are intangible elements that seem hard to explain within ourselves.
How else might a person try to explain the psychological aspect of the human mind, except with theories? Most true psychological measurements are made based upon assumptions about collective behaviour and in fact behaviour seems to be the only real concern of mainstream psychology, but...what about the ideas that influence the behaviour?
In truth MBTI only claims reality through the people that use it. I do not see it as an absolute truth, more than anything I see it as a tool created to induce a sense of inner inspection, especially in those ill inclined to do so, so that people may look at themselves and examine their behaviour and foibles, so that we may understand ourselves and better our relationships and like a drop wearing down a stone, slowly become aware of the automated responses of our minds.
For me THAT is the illusion, to fall into the trap of a response you were induced to by habit and environment, that is a bigger lie than any pseudo-psychological theory.
Unfortunately MBTI is not entirely satisfying, as you said there is no real proof for it. But what to replace it with? Mainstream psychology is just as riddled with collective assumptions about how people act, it assumes that people are born from a singular template and that they are then imprinted on. There is an element of truth to this as in nurture-nature, but it does not go deep enough, nor does it explain the real mysteries of our minds.
Perhaps the big 5 with it's more accepted generalised traits, traits so general they could to apply to any person at any moment without boxing them in. But also without really explaining anything other than an individuals mood at any given time.
So I don't follow MBTI as a blind religion, but I also don't blindly disregard it because it cannot provide empirical evidence about a subject of which there is very little empirical evidence and what's more, very little ways currently of measuring it empirically.
The human mind is a strange creature...we do need to understand ourselves better. Maybe one day we will.
Although don't believe that I disregard evidence that has been proven beyond a doubt. Science is much more useful than MBTI as a measurement of our outward reality, i'm not refuting that. What I am saying is that there are currently limitations.
I would greatly enjoy seeing the day when scientific methodology can truely measure our psyche's, beyond mere behaviourally induced case studies.