Science... if you believe in such a thing.
Here is a critique of MBTI, not Socionics, but the premises of MBTI and Socionics are basically the same, except that some of the orderings are different, etc. They are both based on the Jungian dichotomies, namely the I/E, T/F, N/S and J/P.
The critique is mostly based on scientific enquiry, brain science and more evidence-based psychology:
Goodbye to MBTI, the Fad That Won’t Die - Psychology Today
What are some of the main problems? Brain science says, they are based on false dichotomies:
It ignores your key features in your personality traits that already exist:
There is another problem, Jung's theories aren't exactly based on science:
Weaknesses of Carl Jung's Theory
Okay, so what is actually based on science and backed up by science? Although not perfect, there seems to be growing support and scientific evidence for the Big Five:
So, there you go. Amazing and insightful insights from the world of brain science.