Why has G-d ignored the pleas of the Jewish people for redemption over the past 2,000 years?

This question, in a slightly different form, is asked in the book “Shnei Luchot Habrit,” by Rabbi Yeshaya Halevi Hurwitz. “The sages say: ‘G-d does not reject the prayers of a multitude.’ Yet we see that it is not so! Every day, three times a day, the Jewish people pray eighteen blessings, including many prayers for redemption. Behold our affliction... Sound the great Shofar... Restore our judges... Return us to Jerusalem... And yet, for over 1500 years (as of this writing) we are still in exile!”

He then offers the following explanation: “G-d hears our prayers and the angels fashion them into a crown for Him. However, He does not necessarily carry out the request exactly as we asked. The prayer reached its destination and the reward is still to come.”

In other words, the prayer has its effect up above, even if we don't see immediate results down here below. The Lubavitcher Rebbe explains that since our primary existence is our spiritual soul and not our physical body, the spiritual effect is not incidental, but rather, it is the priority.

At the same time, though, when we pray we don't have in mind a spiritual effect. When we ask for redemption, obviously we are asking for a redemption that will be felt on the physical plane. Our sages have established the prayers for redemption as part of the daily blessings. Therefore, it is understood that the blessings will be fulfilled - otherwise, they would be vain blessings, and we are forbidden to take G-d's name in vain.

How will the blessings be carried out? G-d will link our prayers to the prayers of the hundreds of previous generations. In their merit, we will experience the immediate redemption.

(Shnei Luchot Habrit, 251:1. Igeret Hateshuva, ch. 1. Torat Menachem 5744, p. 781, 817)