The book of Proverbs says simplicity is bad because it leads naïveté and gullibility.
Psalms says God protects the simple hearted.
Jesus said those who are like children are greater than those who are jaded and cynical like older adults.
The Pauline Epistles says a mature adult abandons child like ways.
So how does one reconcile the two views? The way I see it is, you must be simple when your situation calls for simplicity of heart. And you must be complex when your situation calls for complexity of mind.
What the bible teaches is you should be simple hearted in your intention and love and complicated in your analytical and critical thinking skills.
I know many people who are incredible intelligent, with I.Q.‘s in the 99.99th range who are willing to put total faith and trust in friends they seem to be righteous. And I know people with I.Q.’s in the 70’s range who are more complicated than rocket science in their social skills and methods of dealing with people. Not able to graduate high school due to failing grades, but able to tell lies so complicated that even lawyers would believe them.
Not everybody will like you if your simple hearted. But good people and intelligent people will like you if your simple.