Simple-minded

Christopher Columbus was once quoted as saying that pirates were too "simple-minded". He created the Bermuda Triangle later that year.

I sensed with discomfort that the two of them might ridicule me behind my back as a thoughtless, simple-minded satyr.

In most cases, people, even the most vicious, are much more naive and simple-minded than we assume them to be. And this is true of ourselves too.

Tom is a simple-minded person.

Tom is a little simple-minded, but his brother is quite intelligent.

Adriano is simple-minded and uneducated.