The whole idea of man is basically good is baloney because the Bible warns of the fallen nature of man. Jeremiah 17:9 has the Bible call the heart as something that is desperately wicked or deceitful above all things. There is really the terrible truth about the evil of the unregenerate heart. With what Jesus said in Matthew 7:15-20, we really read the sad truth that a bad tree cannot bear a bad fruit. The unregenerate heart is a bad tree that cannot bear good fruit - it may perform works but they cannot be considered good because they are not for the greater glory of God. The unregenerate heart welcomes sin with open arms because it is fallen and needs to be regenerated.
Romans 1:21-31 for ten verses warns of the evils of the unregenerate heart. When the foolish heart is darkened the consequences follows namely (1) professing to be wise to be fools, (2) they have worshiped the creation instead of the Creator, (3) they are given up to their lusts that make them dishonor themselves in many ways given up to vile affections, likewise that even people of the same gender are doing it among themselves as one of the consequences, (4) they do not want to retain God in their knowledge so they are given over to a reprobate mind, and (5) they are now filled with all types of characteristics of the sinful man because they are filled with unrighteousness where people are sexually immoral, wicked, covetous, malicious, envious, murderous, bickerers, deceitful, bearing false witness, spreading gossip, backbiting, hating God, despiteful, arrogant, braggart, inventors of evil things, disobedient to parents, without understanding, no word of honor, no natural affection, implacable, unmerciful as a lifestyle that shows that a person is in desperate need of salvation.
I cannot deny that there are morally good people who are unregenerate in God's eyes but such people will be exposed as doers of iniquity in the Last Day. If they are not living so lewdly they might be involved in some form of wickedness such as doing the right thing to save one's self or the worship of idols. Nobody can say, "Well I can enter Heaven for keeping most of the Commandments." because in God's standard, even one sin is enough to kick a person out of the Book of Life. Deuteronomy 31:26 says that the Book of the Law is a witness against sin. Romans 3:19 says that by the Law of God, all are held guilty before God. If you are angry without a cause, you have been guilty of murder before God's eyes. if you look at a woman with lust, you are guilty of adultery. The more I look at God's Law, the more I realize that I did not deserve salvation and that when I don't want to live a sinful life, it's only because of God's grace (Ephesians 2:8-10, Titus 2:11-14).
There is no way that a lost sinner can do regenerate one's heart himself or herself, as Psalm 73:13 declares that washing the heart was in vain. Proverbs 20:9 says that nobody has kept their heart pure. Fortunately God has a remedy for the unregenerate heart of lost sinners who are broken and repentant. Ezekiel 11:19-21 and 36:26-27 says that a new heart is given to the believer. What happens is that the heart of stone is replaced with a heart of flesh and the Spirit of God is placed into them. The sweet Holy Spirit in John 16:8-9 has the Holy Spirit rebuke of sin which in turn will make the person walk in God's statutes and keep His statutes and do them. What the natural man is incapable of, God's grace makes them capable to overpower any sin by His Holy Spirit.