simpleminded

simpleminded /ˌsɪmpəlˈmaɪndəd/ adjective
simpleminded
/ˌsɪmpəlˈmaɪndəd/
adjective
Britannica Dictionary definition of SIMPLEMINDED
[more simpleminded; most simpleminded]
1 
: not very intelligent
2 
: having or showing a lack of good sense or judgment