Adjectives

(a)naive, naifmarked by or showing unaffected simplicity and lack of guile or worldly experience“a teenager's naive ignorance of life”, “the naive assumption that things can only get better”, “this naive simple creature with wide friendly eyes so eager to believe appearances”
(s)primitive, naiveof or created by one without formal training; simple or naive in style“primitive art such as that by Grandma Moses is often colorful and striking”
(s)naiveinexperienced
(s)uninstructed, unenlightened, naivelacking information or instruction“lamentably unenlightened as to the laws”
(s)uninitiate, uninitiated, naivenot initiated; deficient in relevant experience“it seemed a bizarre ceremony to uninitiated western eyes”, “he took part in the experiment as a naive subject”