This freedom to choose God and repent of our sins through the power of the Atonement is not given to only a few whom God elects to save while all others are thrown into hell with never a whisper of hope. The true and living God is so sovereign, and the Atonement of His Son is so efficacious and powerful, that it can break down all barriers, breaking down the very gates of hell (Hades) to offer redemption to all those who will gladly accept it, to all those who will have faith in the Savior of the world. Those who limit God's love and desire to save to only a select few who lived after the time of Christ are missing the true sovereign power of God and fail to understood how great His mercy is. As the scriptures teach, He wants all to be saved. He gave His Son as a ransom for ALL, across all cultures, continents, and eras of time (1 Timothy 2):
3 For this is good and acceptable in the sight of God our Saviour;That passage of scriptures is consistent, of course, with 2 Peter 3:9 where we read that God is "not willing that any should perish, but that all should come to repentance." That doctrine is better understood in light of the mission of Christ into the spirit world (1 Peter 3:18-20 and 1 Peter 4:6) to preach the Gospel to those who had died. This concept, restored through revelation to the prophet Joseph Smith and later to Joseph F. Smith (Section 138 of the Doctrine and Covenants), along with the attendant blessings of the Temple, baptism for the dead, and other sacred concepts pertaining to the amazing grace and mercy of our most sovereign God, was largely lost from mainstream Christianity for centuries.
4 Who will have all men to be saved, and to come unto the knowledge of the truth.
5 For there is one God, and one mediator between God and men, the man Christ Jesus;
6 Who gave himself a ransom for all, to be testified in due time.
7 Whereunto I am ordained a preacher, and an apostle, (I speak the truth in Christ, and lie not;) a teacher of the Gentiles in faith and verity.
I encourage you to understand the early Christian roots of these restored LDS doctrines and practices. It is a testimony-building experience to contemplate the evidences for the Restoration and the wondrous, true mercy of God in providing means that all who will accept grace may receive it in the covenants and blessings He offers.
A great summary of information about early Christian concepts in this area can be found in two recent publications from the Maxwell Institute. Please see "The Harrowing of Hell: Salvation for the Dead in Early Christianity" by Kendel J. Christensen, Roger D. Cook, and David L. Paulsen and "Baptism for the Dead in Early Christianity" by Brock M. Mason, and David L. Paulsen. These are intelligent, interesting, scholarly articles that will help you better appreciate some of the reasons why we Mormons are so excited about the broad, broad scope of the Atonement of Jesus Christ and the tools God has given us to participate in bringing the Gospel to His sons and daughters across the expanses of geography and time. Free agency and infinite mercy made available to all who will choose it--now that's a sovereign God.