You are misunderstanding this passage. A few verses earlier it says:It is written..."The soul that sinneth, it shall die. The son shall not bear the iniquity of the father, neither shall the father bear the iniquity of the son: the righteousness of the righteous shall be upon him, and the wickedness of the wicked shall be upon him." (Ezek 18:20)
Eze 18:2 "What do you mean when you use this proverb concerning the land of Israel, saying: 'The fathers have eaten sour grapes, And the children's teeth are set on edge'? 3 "As I live," says the Lord GOD, "you shall no longer use this proverb in Israel.
The people were saying this because of direct sayings in the Scriptures.
2 Kings 24:2 And the LORD sent against him raiding bands of Chaldeans, bands of Syrians, bands of Moabites, and bands of the people of Ammon; He sent them against Judah to destroy it, according to the word of the LORD which He had spoken by His servants the prophets.
24:3 Surely at the commandment of the LORD this came upon Judah, to remove them from His sight because of the sins of Manasseh, according to all that he had done,
They understood that it was saying that they were being raided by the Chaldeans because of the sins of Manasseh.
It says the same thing in Jeremiah:
Jer 15:4 I will hand them over to trouble, to all kingdoms of the earth, because of Manasseh the son of Hezekiah, king of Judah, for what he did in Jerusalem.
Same thing in Lamentations:
Lam 5:7 Our fathers sinned and are no more, But we bear their iniquities.
That is why they came up with the saying: 'The fathers have eaten sour grapes, And the children's teeth are set on edge'
In Ezekiel 18, God is telling them that if they had repented and changed, it would not have happened. Yes, this builds up and God's anger gives people time to repent, and if they had repented, then what Manasseh had done wouldn't effect them.
But this is totally different than God making one man (Adam) and giving him the office of head of the human race and making a covenant with him and only one law (don't eat from this one tree) and when Adam did eat from it, he broke the covenant for himself and all his posterity.
Like I said, if you reject this, you also reject the fact that Jesus acted on behalf of His people (fulfill the law and pay the penalty of death) and we are declared non-guilty based on what He did.
It doesn't say they have not sinned. It says: who had not sinned according to the likeness of the transgression of AdamWhy then, does it mention those who have not sinned ? (Rom 5:14)
Here is a clearer translation:
Romans 5:13-14
New Living Translation
13 Yes, people sinned even before the law was given. But it was not counted as sin because there was not yet any law to break. 14 Still, everyone died—from the time of Adam to the time of Moses—even those who did not disobey an explicit commandment of God, as Adam did.
Everything God says is sin now, was still a sin back then, even though God had not specifically spelled it out. They lied and and a thousand other things we know are sin, but at that time there was no specific command not to do it.