The bulk of it is indeed prophecy (chapters 6-21). But the letters to the seven churches (chapters 1-3) are warnings and commendations to each of those churches in Asia Minor (now Turkey). And what is said in those letters has applicability to all churches today. Let's look at the warnings and how they apply to churches today.
WARNINGS
1. Nevertheless I have somewhat against thee, because thou hast left thy first love. Remember therefore from whence thou art fallen, and repent, and do the first works; or else I will come unto thee quickly, and will remove thy candlestick out of his place, except thou repent.
2. But I have a few things against thee, because thou hast there them that hold the doctrine of Balaam, who taught Balac to cast a stumblingblock before the children of Israel, to eat things sacrificed unto idols, and to commit fornication. So hast thou also them that hold the doctrine of the Nicolaitans, which thing I hate. Repent; or else I will come unto thee quickly, and will fight against them with the sword of my mouth.
3. Notwithstanding I have a few things against thee, because thou sufferest that woman Jezebel, which calleth herself a prophetess, to teach and to seduce my servants to commit fornication, and to eat things sacrificed unto idols. And I gave her space to repent of her fornication; and she repented not. Behold, I will cast her into a bed, and them that commit adultery with her into great tribulation, except they repent of their deeds. And I will kill her children with death; and all the churches shall know that I am he which searcheth the reins and hearts: and I will give unto every one of you according to your works.
4. And unto the angel of the church in Sardis write; These things saith he that hath the seven Spirits of God, and the seven stars; I know thy works, that thou hast a name that thou livest, and art dead. Be watchful, and strengthen the things which remain, that are ready to die: for I have not found thy works perfect before God.
5. Behold, I will make them of the synagogue of Satan, which say they are Jews, and are not, but do lie; behold, I will make them to come and worship before thy feet, and to know that I have loved thee... Behold, I come quickly: hold that fast which thou hast, that no man take thy crown.
6. Because thou sayest, I am rich, and increased with goods, and have need of nothing; and knowest not that thou art wretched, and miserable, and poor, and blind, and naked: I counsel thee to buy of me gold tried in the fire, that thou mayest be rich; and white raiment, that thou mayest be clothed, and that the shame of thy nakedness do not appear; and anoint thine eyes with eyesalve, that thou mayest see. As many as I love, I rebuke and chasten: be zealous therefore, and repent.
So what we see here is that every church which claims to be Christian today must address: (1) failure to love God and Christ perfectly, (2) false doctrines, (3) false practices, (4) toleration of sin, evil, and heresy within the church, and (5) unconverted church members.