So, I did a word search on simple and here are the results (RSV):
Job 5:2, "Surely vexation kills the fool, and jealousy slays the simple.
In the Psalms:
19:7--The law of the LORD is perfect, reviving the soul; the testimony of the LORD is sure, making wise the simple; 116:6--The LORD preserves the simple; when I was brought low, he saved me. 119: 130--The unfolding of thy words gives light; it imparts understanding to the simple.
In the Proverbs:
1:4--that prudence may be given to the simple, knowledge and discretion to the youth-- 1:22--"How long, O simple ones, will you love being simple? How long will scoffers delight in their scoffing and fools hate knowledge?" 1:32--For the simple are killed by their turning away, and the complacence of fools destroys them; 7:7--and I have seen among the simple, I have perceived among the youths, a young man without sense; 8:5-- O simple ones, learn prudence; O foolish men, pay attention; 9: 4--"Whoever is simple, let him turn in here!" To him who is without sense she says; 14:15--The simple believes everything, but the prudent looks where he is going; 14:18--The simple acquire folly, but the prudent are crowned with knowledge; 19:25--Strike a scoffer, and the simple will learn prudence; reprove a man of understanding, and he will gain knowledge; 21:11--When a scoffer is punished, the simple becomes wise; when a wise man is instructed, he gains knowledge: 22: 3--A prudent man sees danger and hides himself; but the simple go on, and suffer for it.
Romans 16:18 --For such persons do not serve our Lord Christ, but their own appetites, and by fair and flattering words they deceive the hearts of the simple-minded._______________________________________________
The Bible is not flattering about anything or anyone "simple." They are warned to leave behind their simpleness and learn wisdom.
We do know that the Bible talks to us about Christians being like little ones and sheep, but obviously they are not to be simple-minded. Paul in I Corinthians warns the people to leave behind the milk and get on to learning the meat.
Peter talks about the hard writings of Paul.
God gives us teachers especially graced with knowledge in order to convey the meaning of the gospel and scripture.
Sounds to me as if "simple" would not be an accurate characterization of the gospel nor of God himself.
Ps. 92:5, "How great are thy works, O LORD! Thy thoughts are very deep!"
Isaiah 55: 8-9, "For my thoughts are not your thoughts, neither are your ways my ways, says the LORD. For as the heavens are higher than the earth, so are my ways higher than your ways and mythoughts than your thoughts."
When you study the string theory of physics and molecular biology, watch a child being born, categorize bugs, study psychology and history it is hardly simple, in fact, the more you know the more complex things become. God is not simple, neither is His gospel.
Jesus revealed a mystery known from the beginning, a mystery so deep and so complex that His disciples could not begin to understand it, even after spending three years with Christ. It is so unfathomable that the truth of the gospel cannot be revealed but by the Father through the Holy Spirit.
To call Christ's sacrifice simple, is a desire to make it easy--to make is casual--to make it common. The gospel's complexity is resplendent and magnificent. It is so full of fearsome, breathtaking and staggering beauty that all who see its glory fall on their knees and exclaim, "holy, holy, holy Lord God almighty!"