Repentance toward God is much bigger than repenting of sins. But repenting of sins is part of it.
Sinning brings on God’s wrath. Repentance involves recognizing this great danger, and the need to be saved from it. That prepares the way for the Savior, Jesus. That makes a person’s heart ready to receive Christ. Those who are not aware of this danger are not ready to hear the Gospel. Who would go running out of their house in the middle of the night, if they were unaware the house was on fire?
Romans 2:5 KJV
[5] But after thy hardness and impenitent heart treasurest up unto thyself wrath against the day of wrath and revelation of the righteous judgment of God;
Not only that, we must warn them of the wrath that is affecting them even now.
Romans 1:18 KJV
[18] For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness;
Colossians 3:6 KJV
[6] For which things' sake the wrath of God cometh on the children of disobedience: