Why did it take the Abrahamic God so long to reveal His plan for mankind?

According to the books that lay out the claims for God’s existence, whether we read the Torah, Bible or Koran, he is both omnipotent and omniscient. So one might think he’d be able to figure out how to communicate his plan to man in one sitting. But that did not happen. There are many differing accounts of how long the whole revelation process took. It depends on which of the many Abrahamic religions you consult.

To Jews, the process runs from God’s first communication with Adam and Eve about 6,000 years ago through revelations to Noah—Genesis 6:9–18:15, Abraham & Sarah—Genesis 11:31–19:9, Isaac—Genesis 26:2 & 24, Jacob—Genesis 35:1 & 9, Moses (the greatest of prophets), David—2 Chronicles 3:1, Solomon—2 Chronicles 1:7 & 1 Kings 3:5 & 9:2, Elijah—1 Kings 17:1 & 19, Elisha—2 Kings 2:1–15, Jeremiah—Jeremiah 25:15 & 31:3, Isaiah—Isaiah 6, and Daniel—Daniel 8:15 & Daniel 10. Now that leaves out a lot of the Prophets, but those are the important ones. And that revelation would stretch over a period of from about 4,000 BCE to perhaps 300 BCE, a period of some 3,700 years.

Christians claim that in that 3,700 years, God never worked out how to deliver his full message to mankind. To get the whole story to us, God further appeared to Mary and Joseph, then gave them a child by immaculate conception, that child being God himself in a different person that was the same person. Jesus lived for 33 years working on getting the message straight with humanity. But after Jesus’ Crucifixion and Resurrection to walk with his disciples another 40 days, God still had to appear to Peter and Paul to further refine the message. So now we’re getting close to 4,100 years of work on communicating God’s wishes for man.

Muslims, on the other hand, hold that Jesus was just another in the line of prophets, and that Muhammad was the Final Prophet who delivered the Total Word of God in the form of the Koran in 632 CE. Now we’re up to 4,623 years to deliver the message.

Then we have the outliers such as Christian Scientists, Mormons, etc. who insist that God still hadn’t gotten things right and only managed to finish the work when their particular founder wrote the final chapter within the past few decades, meaning it took God the better part of 6,000 years to write 1 book. Good thing he’s omnipotent and omniscient, or it might have taken some seriously long time to finish the task. Good thing he’s eternal, too. He’d never be a published author of he had to do it in the few short years allotted to ordinary human writers. Why do you think it took so long? Are we there yet, or is he coming back for yet anther pass and completing the message?