The Medrash tells us that Knesses Yisroel tells Hashem that Tshuva is Hashem's. Hashem responds that Tshuva is ours like it says in the Pasuk "Shuvu Eilai V'Ashuva Eileichem". What is the meaning of this Medrash?
The Shir Ma'on, Rav Shimon Sofer the son of the Ksav Sofer, says that the pasuk says "Karov Hashem L'Chol Kor'ov", Hashem is close to all those why call out to him (Tehilim 145:18). So why do we call out and are not answered? Because we do not call out for Hashem, only for ourselves. Hashem guarantees an answer only for those who call out for His honor.
Our purpose in crying for the geula, says the Shir Maon, is to be able to serve Hashem in the Bais HaMikdash. The Hamon Am call out for Moshiach when they are hungry and in pain. If we'd call out for Moshiach the right way he would have long ago been here.
This is pshat in the Medrash. Klal Yisroel tells Hashem that we do Tshuva for Him, for His honor. Hashem disagrees and says that our tshuva is for ourselves to extricate ourselves from our Tzorus. "Shuvu Eilai V'Ashuva Eileichem", if you really did tshuva for me, I would have immediately returned to you.