Your translation in my opinion is closer to the definition of 눈치 없다.
Just as I think 눈치 있다 should be interpreted as "savvy", 눈치 없다 should be interpreted as "imperceptible" which does not indicate a low IQ (low EI, emotional intelligence perhaps)
Slow-witted on the other hand means low IQ. Wrong choice for word.
The subject is not given. It copuld just as easily been "Why am I slow witted." Asking a Korean this question to his or her face is about the biggest insult I can think of and would likely end any friendship or relationship. It is a 큰 일! You're calling them stupid!!!
The answer should be changed or the statement should be remomoved.