WISDOM OF GOD AND FOOLISHNESS OF THE WORLD
1Corinthians 1.17-31
Here Paul started that he teaches in not elaborate way or in very sophisticated and complicated style but in simple words for the people to understand and to learn the secrets of GOD'S Word.
On the other hand, it is true that some writings of Paul a little bit complicated which has been noticed by Peter and others (2Peter 3.15-16). Complication (in some cases) of Paul writing also may be explained by his attempt to reach also and more educated people among population and leaders of Israel, and he did accomplish it to some extent.
Complicated writings of Paul may also be due to numerous translations and revises of the Bible in the past and even today by many different scholars who are themselves not always fully understood Paul's intent in some of his statements and used they own understanding or their doctrinal policies to figure out Paul's intent.
Under "cleverness of speech" (17.19) Paul certainly meant demagogy and meaningless theology of many preachers whose goal only to impress the audience with their "bombastic nonsense." NRSV. (2Peter 2.17-19) and nothing else.
"arrogant words of vanity." KSB.
"great swelling words of vanity." KJV.
"great swelling words of emptiness." Gideons.
"boastful words." NIV.
"loud boasts of folly." ESV.
"They make proud and stupid statements." GNB
But the wisdom given from GOD to those who deserve it and who called to teach is completely different from those who teach from themselves. As it written in verse 2 "have been sanctified in Jesus Christ, saints by calling" these are the true teachers of the Word of GOD who teach people according to the Spirit of GOD and His Gospel without any demagogy, theology, and "cleverness of speech," not to impress people with their convoluted speech but to save souls for GOD.
Indeed, wisdom of GOD in this world is considered as foolishness, and foolishness of this world considered as wisdom. But if we boast, we shall boast only in the wisdom of GOD and His glory, for His mercy, love, faith, and the power of deliverance All Mighty Lord (verse 31). (Psalm 20.7, 44.8) (Jeremiah 9.23-24) (1Corinthians 1.31) (2Corinthians 10.17) (Galatians 6.13-14).