The Amplified Bible renders I Corinthians 1:17: "For Christ, the Messiah, sent me out not to baptize but (to evangelize by) preaching the glad tidings (the Gospel): and that not with verbal eloquence, lest the cross of Christ should be deprived of force and emptied of its power and rendered vain -- fruitless, void of value and of no effect." The Apostle Paul is saying that there is a way of preaching the gospel that is not really preaching the gospel at all!
The gospel is often cloaked and concealed from men in the lofty phrases of intellectualism. True things are preached but in a way to impress men rather than to save them. The gospel is made of no effect by detailed word studies that show the preacher's learning or by words that the average hearer has no understanding of. The message of the text is lost in the detail of the elements studied. The sermon is full of historical information, laden with references to the old creeds, confessions and writers and dotted with numerous clever illustrations. It is void of any heart-felt declaration of the Person and work of the Lord Jesus.
Likewise many sermons are simply the platform for the advancement of a social cause or the defense or denial of a social or political issue. Preachers speak much of being "Christ-like." They denounce with great fervor the moral errors of our day. But they don't preach Christ. They don't preach the gospel which God alone uses to produce all true godliness. There is always a "fight" to challenge the people to take up. Sadly, even many good things become the enemy of the best.
It is also true that many have made the gospel of no effect to their hearers by an emphasis on prophetical subjects. The coming of Christ becomes more important than the Christ who has already come, accomplished salvation for His people and Who will come again. Various prophetic positions are taught in great detail involving much time and the Gospel of Christ goes wanting one to proclaim it.
Then there is the matter of emotionalism. Often, how something is said is more important that what is said. Men look more at how one preaches than what he preaches. Loud and dogmatic is thought to be the Spirit's empowerment. Any truth that might be preached cannot be heard for the loud displays of fleshly enthusiasm. What men call spiritual has nothing to do with the Spirit of God who testifies of Christ.
Lord help us not to preach a gospel of no effect! Paul said, "I am determined to know nothing among you save Jesus Christ and him crucified." The gospel plainly, repeatedly and without distractions or enhancements alone is used of God to save His people. A gospel that by these things is made of no effect is no gospel at all!