No, I did not say those people would not enter heaven, and I confess to being surprised at the question, but you are right about the thief on the cross. A murderer was released instead of Jesus.
My point was that the thief was not baptised, yet was promised paradise. You implied he was under the Old Covenant, which if he was bound by law, would demonstrate his eternal guilt!
But lets go way back beyond Abraham and Enoch and all the way to Adam.
Ever since creation, anyone who called on the name of the Lord could be eternally saved by faith.
Galatians3v6Even as Abraham believed God, and it was accounted to him for righteousness. 7Know ye therefore that they which are of faith, the same are the children of Abraham. 8And the scripture, foreseeing that God would justify the heathen through faith, preached before the gospel unto Abraham, saying, In thee shall all nations be blessed. 9So then they which be of faith are blessed with faithful Abraham.
Even though Adam was many generations earlier, the same principle spoken about Abraham applies to him and all his descendants. By children of Abraham, it just means they are children by faith, not law.
John1v1In the beginning was the Word, and the Word was with God, and the Word was God. 2The same was in the beginning with God. 3All things were made by him; and without him was not any thing made that was made.4In him was life; and the life was the light of men. 5And the light shineth in darkness; and the darkness comprehended it not.......................................
.....................1John1v12But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name: 13Which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God.
This is about believing and putting your trust in the word/logos who is and was God, God who created all things, the light of the world. All of them are sons of God. That means all the ancient patriarchs etc were born again long before Jesus mentioned it in John3.
New birth was true for Abel, who obviously wasn't an Israelite, nor under the law of Moses, and also true for Zechariah, and for me and you.