one's elevator doesn't go all the way to the top
/wʌnz ˈɛləˌveɪtɚ ˈdʌz.ənt ɡə ɔːl ðə weɪ tʰu̟(ː) ðə tɒp/
someone lacks common sense or understanding.
“He thinks he’s funny, but his elevator doesn't go all the way to the top.”Add to my deck
inoh