Of course false prophets exist. They have existed in past generations and they exist today. Justin Martyr, writing only a couple of generations after the Resurrection of Jesus Christ, declared:

And just as there were false prophets contemporaneous with your holy prophets, so are there now many false teachers amongst us, of whom our Lord forewarned us to beware; so that in no respect are we deficient, since we know that He foreknew all that would happen to us after His resurrection from the dead and ascension to heaven. For He said we would be put to death, and hated for His name’s sake; and that many false prophets and false Christs would appear in His name, and deceive many: and so has it come about. For many have taught godless, blasphemous, and unholy doctrines, forging them in His name (in AnteNicene Fathers, 1:240).

The Old Testament alludes to an apostasy from truth prior to Christ’s second coming. The New Testament furnishes significant evidence both predicting an apostasy and confirming that it had already begun while the Apostles were still alive, teaching the gospel that they had been taught by the Master Himself.

Many in the Church were rejecting Jesus’ teachings for portions of the old Jewish law, selected pagan practices, and various Greek philosophies. This apostasy was brought about by fading priesthood authority followed by false doctrinal innovations. Thus, the authority to perform the rites and sacraments disappeared.

Clearly the prophecies recorded in scripture were reliable: a general apostasy from Jesus’ gospel had left behind only a dead form of a church without the living Spirit of truth.

Sources

Where Have All the Prophets Gone? Scott R. Petersen