Probably today's false teachers are aren't more numerous than they were in the first century, though it feels like they are. Apologist James R. White said today
there are not more heretics today, there is just more availability of making your heresy known.
Like ants at a picnic, these false teachers are everywhere, and more are popping up every day. Jesus is in control and has ordained each and every one. As He does with everything, He has a purpose for false teaching.
What Is God's Purpose With False Teaching? asks and answers John Piper.
Or this, from Dr. Paul M. Elliott, "Why Does God Permit False Teachers in the Church?"
God uses the response to false teaching on the part of the members of the visible church, individually and corporately, to demonstrate who is true to Him and to His Word, and who is not. To put it another way, God is building a record that Christ will use at the Last Judgment, when many will come before Him and claim to have done many wonders in His name, but Jesus will say, "I never knew you; depart from Me, you who practice lawlessness!" (Matthew 7:23).The main reasons God permits false teachers is that first, sin exists in the world. False teaching is sin. Secondly, it's used to test His people. So though it's a grief, a burden, and a scourge, God has His purposes for allowing it.
And then sweet relief will come! There will come a day when false prophets will not be allowed!
After the rapture, and after the conclusion of the Tribulation, in that order, a Kingdom on earth will be established. It will last for 1000 years. It is colloquially called the Millennium Kingdom. It will be an actual kingdom whereupon incarnated Jesus walks among His people, rules from Jerusalem, (Revelation 2:27) administers affairs of the nations, and receives worship (including sacrifices) in the Temple. (Isaiah 56:6-8; Zechariah 14:16; Jeremiah 33:15-18, Ezekiel 43:18-46:24)
Satan will be bound in the pit along with his demon horde. (Revelation 20:1-3). The people occupying the Kingdom will have relief from satan, finally! However, sin will still be present. Some of the people who survived the Tribulation will be mortal, and thy will enter the Kingdom along with us (glorified at the rapture) and the Old Testament saints (resurrected at the end of the Tribulation) and Tribulation martyrs (resurrected at the end of the Tribulation). These mortals will repopulate the earth through procreation, and their children will do the same and so on, for 1000 years. These mortals will still have a sin nature, which will express itself at the end of the 1000 year kingdom when satan is released from the pit and gathers the secretly sinful like sands upon the sea to rebel against Jesus. (Revelation 20:7-8).
But meanwhile during the blissful 1000 year Kingdom, there will be no false teaching, no false teachers, no false prophecies!
"And if anyone again prophesies, his father and mother who bore him will say to him, ‘You shall not live, for you speak lies in the name of the LORD.’ And his father and mother who bore him shall pierce him through when he prophesies." (Zechariah 13:3)
The form of phraseology here is drawn from De 13:6–10; 18:20. The substantial truth expressed is that false prophecy shall be utterly abolished. If it were possible for it again to start up, the very parents of the false prophet would not let parental affection interfere, but would be the first to thrust him through. Love to Christ must be paramount to the tenderest of natural ties (Mt 10:37). Much as the godly love their children, they love God and His honor more. (Jamieson, R., Fausset, A. R., & Brown, D. Commentary Critical and Explanatory on the Whole Bible)The dance between false prophets and demons will end. Matthew Henry:
False prophecy shall also be brought to an end: I will cause the prophets and the unclean spirit, the prophets that are under the influence of the unclean spirit, to pass out of the land. The devil is an unclean spirit; sin and uncleanness are from him; he has his prophets, that serve his interests and receive their instructions from him. Take away the unclean spirit, and the prophets would not deceive as they do; take away the false prophets that produce sham commissions, and the unclean spirit could not do the mischief he does. When God designs the silencing of the false prophets he banishes the unclean spirit out of the land, that wrought in them, and was a rival with him for the throne in the heart. Henry, M. (1994). Matthew Henry’s commentary on the whole BibleOf the Zechariah 13:3 verse, John MacArthur comments:
Because of the salvation of God that has cleansed God's people and made them love Him and His truth, hatred of false prophecy will overrule normal human feelings, causing even a mother or father to put their apostate child to death. This is a stern reminder of hos God feels about and will eventually treat those preaches who misrepresent the truth.Contrast the Zechariah verse of Millennium parents killing their own child because he speaks false prophecy, to the verse in Matthew 10:21 when in the last days parents will kill their offspring for speaking the Truth.
What a time that will be! When love for Jesus and His truth is the worldwide global attitude! For all my brethren who read this, it's an essay about prophecy, obviously. It is also encouragement. Jesus IS in control. He has a plan, and that plan includes the [hopefully soon] day when He will rule and reign personally and false prophets will not be tolerated. What a day that will be.