Where do the Jews play a role in G-d’s plan?

“Israel has not fulfilled in any measure its role to be a priestly nation for over 2,000 years. That’s the charge against G-d’s people.” I would say that such a charge is saying that G-d made a mistake when choosing the Jewish people , no?  Oh No! is the reply, G-d HAS a purpose for the Jews……. yet to be seen in the future.

OK, so let me ask you, what was the purpose of the nation of Israel from 400 ce –  1500 ce in G-d’s plan? To prove that G-d can preserve a nation?  Is this a silly game where Israel is just a guinea pig so G-d can prove Satan wrong?  The Jews are butchered just to prove a point?  Were the people of G-d just put on earth so that they can reject Jesus so that…