Trying to change people is very hard. The old saying; "You can lead a horse to water, but you cannot make him drink." This is true when it concerns the teaching of the gospel of Christ. The church can introduce people to the word of God; but have no power about getting men to embrace it.
Noah preached for many years while he was also preparing the ark. The world in which Noah lived, was full of brick head people and he didn't gain one convert. The only people saved from the flood were the eight people who lived in his house. Everyone thought Noah was crazy so they didn't listen to him. 2 Peter 2.5. 1 Peter 3.20 Gen 7.5-11