I guess its hardly a surprise that there was a need for Christ to come and sort it all out. The questions that need to be answered is why would Yahweh be content for 100 generations to live and die under "beta-test" rules?
Subsidiary question: In 5BCE, people living and dying would be "judged" by Yahweh under the old rules. As we run through the years around 30CE, we would get a mix of people dying. Some would know nothing about the OT. Some would have heard all about the New Covenant and be judged by it. And, of course, the group living twenty miles outside of Galilee who heard some vague stories about this preacher with the new ideas, but not really understood them or had heard them all.
In the years past 35CE, we could see a ripple effect spreading out from the area. Depending on how far you were from the area, how much you listened to new ideas, you may or may not hear the New Covenant. So what does Yahweh do? The new Covenent exists, its out there, is he still judging people by two seperate standards? Seems weird - if his "New Rules" are all that, then it seems bizarre to accept that some people can be judged on the old rules just because they hadn't yet heard them.
I wonder how Yahweh judged the 90 year old man on his deathbed, born and raised in the traditions of the OT, who hears the New Covenant on the day he dies, but rejects it as he doesn't have the time for it to take hold?
In short, its a big mess. Yahweh changes the rules mid-game for everyone alive at that point. Why change something if its not working? And if its not working, what kind of dumb-ass came up with the unworkable rules in the first place?