You have to remember the Jews killed all their prophets. What is in the OT had to come to pass. It did, when Jesus walked the earth. The Jews were still going to do what they did. They were still going to believe what they believe.
I agree 100%. I would never say truth didn't exist in the OT. Abraham was so intent of seeking god, he did the best he could. Even Jesus said in John, that Abraham would have recognized him. And Moses as well.
But it was a time of angels. Remember, an angel appeared to Joseph Smith. An angel appeared to Mohammad. If we are going to judge angels, they are judged even now by the Gospel message.
Jesus brought clarity of Truth. He came with a sword. He divide those that were his from those that were never his. Fathers, sons. Mothers, daughters.
If we follow Christ, we follow his words, right?
John:
Verily, verily, I say unto you, He that entereth not by the door into the sheepfold,
but climbeth up some other way, the same is a thief and a robber.
John:
7 Then said Jesus unto them again, Verily, verily, I say unto you, I am the door of the sheep.
8
All that ever came before me are thieves and robbers: but the sheep did not hear them.
9 I am the door: by me if any man enter in, he shall be saved, and shall go in and out, and find pasture.
John:
27 My sheep hear my voice, and I know them, and they follow me:
John 10 is one of the greatest identifier of what a Christian is, and why the Jews tried to kill Jesus.
Jesus was the Truth AND the Way. He went back and appeared to all the Jews that has truly sought Truth that were in Hades (the deep sleep). And many saw his light and were saved, and appeared to many (at the Resurrection). That is Gospel. The Jews had died. Now, only Jesus is the door. I don't want to end up where the OT took the Jews, but to only open the door that Christ says he is.
I pray this makes sense, and you see the image.