In the New Testament we have a simple gospel: Who Christ is and what He has done and a call for repentance and faith. There was a simple invitation and there was a simple, but true response.
What we often fail to understand is the context in which the gospel is declared. The context of the gospel in N.T. times was the holy, separated lives of believers who were totally and unreservedly committed to Christ. In that context the simple gospel had great power. Not that the power was in the messenger, but that the lives of those messengers were pleasing to God and it caused the Holy Spirit to move powerfully through them. Many responded in simplicity and their lives were transformed. They also became holy, separated and deeply committed followers of Christ, like those who led them to Christ.
We have the example of Paul. Though he preached to those who did not know him, and they had no context in which to receive the gospel, his life in their midst became the context of the gospel.
"For our rejoicing is this, the testimony of our conscience, that in simplicity and godly sincerity, not with fleshly wisdom, but by the grace of God, we have had our conversation (manner of life) in the world, and more abundantly to you-ward" (2 Corinthians 1:12).
His life demonstrated the love of Christ; his conduct was holy and without blame and his sufferings for Christ, at their hands, demonstrated his total commitment to Christ. Paul preached a simple gospel, he gave a simple invitation, “believe on the Lord Jesus Christ and thou shalt be saved”, and people responded in simple faith and were gloriously saved and transformed. The context of the gospel released the great power of the gospel, and helped define what the gospel is about and what repentance is.
Today, we have lost the right context of the gospel. In the first half of the 20th century believers proclaimed and shared the gospel in the context of separated, holy lives that were totally committed to Christ. That gospel message was simple, the invitation was simple, and people responded and were gloriously saved.
As the century wore on, something happened to the context of the gospel. After WW II, plenty and pleasure began to fill our lives, good times and good things distracted us. For the most part, believers lost separation from the world and with it went holy living and deep commitment to Christ. With that change the context of the gospel was changed. Phil. 1:27a, "Only let your conversation (Life) be as it becometh the gospel of Christ...."
The same simple gospel was declared with the same simple invitation to which some responded, but now, the response largely results in pseudo salvation, the product of powerless easy-believism, and lives which deny God’s Word.
Mass evangelism further destroyed the context of the gospel with apostate liberals on the platform, with movie stars and superstar athletes whose lives were not holy and separated and transformed, and whose commitment to Christ was shallow. TV further destroyed the context of the gospel, with no connection of the message to the lives of the messengers. The need for repentance is denied by unholy lives. "Her priests have violated my law, and have profaned mine holy things: they have put no difference between the holy and profane, neither have they shewed difference between then unclean and the clean...." (Ezekiel 22:26).
Today, even when you share the gospel with those who do not know you, they have in their minds a context of the gospel, sometimes from TV and sometimes from carnal Christians, and that confuses the message, grieving and limiting the Holy Spirit.
The problem is not the message, not the invitation, but the context in which the gospel is presented. We may not be able to restore a right context in the wider church, but we can restore this context in our individual lives, and in our individual churches and trust God to save some!