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Let's face it, the MBTI has its own shortcomings and many of them are additions to Jung's thought. However, I believe it's the most pop system for introducing fundamental topics.
I also saw it as a bit odd at first, but it makes the most sense after thinking about it.
NT vs NF is a good division because intuition and thinking (NT) vs intuition and feeling (NF) are quite distant personality-wise. The former were coined "the rational(ist)s" as all 4 enjoy abstract, nerdy topics like MBTI itself. The latter... cry a lot?
NP vs NJ would've put INTP, INFP, ENFP, ENTP in one group which would be obvious nonsense. INTJ, INFJ, ENFJ, ENTJ in another. Uhhh, nope.
The main thing about the SP vs SJ division is that SPs use Se and SJs use Si. This makes most of the SPs (ISTP, ESTP, ESFP) seem very "JUST DO SHIT" and most of the SJs (ISTJ, ESTJ, ISFJ) seem very chill and or serious/organized.
Grouping sensors by ST vs SF would put ISTJ, ESTJ, ISTP, ESTP in one group, not quite seeing the commonality. ISFJ, ESFJ, ISFP, ESFP would go in another. Same hodgepodge dilemma.
16p's grouping of 4 types in 4 groups seems like a shitty version of socionics' quadras, which group types on common valued/frontstack cognitive functions. But in my opinion that's 16p's problem in general, disregard of the functions just to describe personality. That just seems like no fun at all to me!