Apostasy is about being disconnected from God. Anyone is in apostasy who is not experiencing two-way communication with God.
Some people believe that Apostacy means that there is not a true prophet on the earth or a true church on the earth. This is not the case. We are not saved or exalted because a true prophet walks the earth. We are not saved or exalted because we joined a church with true prophets leading it. Our salvation is not going to happen as a result of someone else living righteously. Our salvation and exaltation are dependant upon our ability to receive the Holy Ghost, hear the voice of God and obey God’s voice to us directly. Only then are we no longer in apostasy from God.
The difference between the wicked and the righteous is that the wicked cannot hear the voice of the Lord while the righteous can.
D&C 84:52-53
52 And whoso receiveth not my voice is not acquainted with my voice, and is not of me.
53 And by this you may know the righteous from the wicked…
D&C 38:6
6 And even so will I cause the wicked to be kept, that will not hear my voice but harden their hearts, and wo, wo, wo, is their doom…
Mosiah 16:2
2 And then shall the wicked be cast out, and they shall have cause to howl, and weep, and wail, and gnash their teeth; and this because they would not hearken unto the voice of the Lord; therefore the Lord redeemeth them not.
The Whole premise of the church is based on personal revelation from the Lord to each member of the church. It is what we tell investigators they can trust above all other sources. Apostacy is overcome when we ourselves can commune with the Lord through the veil.
Those who are still in apostacy rely on others to speak with God for them. They teach that we are not worthy to talk to God and need a prophet who is more worthy then we are.
D&C 1:17
17 Wherefore, I the Lord, the calamity which should come upon the of the earth, my Joseph Smith, Jun., and unto him from heaven, and gave him ;
18 And also gave commandments to others, that they should proclaim these things unto the world; and all this that it might be fulfilled, which was written by the prophets—
19 The things of the world shall come forth and break down the mighty and strong ones, that man counsel his fellow man, neither in the arm of flesh—
20 But that every man might in the name of God the Lord, even the Savior of the world;