The verse does not prohibit more prophesy after John the Immersor, but says that all the previous OT prophets spoke of the days of John.
"for all the prophets and the law till John did prophesy," (YLT)
"All" is Strong's Greek 3956 - πάντες (pantes), defined as all, every.
From Thayer's Greek Lexicon: 2 with a plural - all (the totality of the persons or things designated by the noun)
"All" meant the entirety, the whole of the prophets and the whole of the law.
"Until John" or "till John" marked the time that "all" or the whole of the prophets had prophesied. Christ was speaking of the OT prophets who prophesied of His coming.
The prophets had foretold of the latter days of the coming of the Messiah. That they were until John marked John's generation as the latter days and the fulfillment of those OT prophesies in his generation - the first century A.D.
Ellicott's Commentary on Matt. 11:13,
"(13) All the prophets and the law.—The usual order is inverted, because stress is laid on the prophetic rather than the legislative aspect of previous revelation. They did their work pointing to the kingdom of heaven in the far-off future of the latter days, but John saw it close at hand, and proclaimed its actual appearance." Source: Biblehub
Gill's Exposition on same:
"For all the prophets and the law prophesied until John. These words are to be considered in connection with Matthew 11:11 and are a further proof of John's being greater than any of the prophets; because all the inspired writers and prophets, who were before him, prophesied of the Messiah as to come; and either spoke of him in obscure terms, or represented him under dark shadows and figures: whereas John spake of him as already come, and in plain terms, and directed to his very person; and since his time, there have been no prophecies concerning the Messiah and his kingdom; vision and prophecy are now sealed up; all which are acknowledged by the Jews themselves, who (b) say, , "all the prophets did not prophesy but to, or of the days of the Messiah". This was the subject, and these the limits of their prophecies; for they own (c), that "from the day that the temple was destroyed, , "prophecy was taken away from the prophets".''
"Since that time, they confess they have had no prophet (d), and that they are not able to observe their signs.
"(b) T. Bab. Beracot, fol. 34. 2. Sabbat, fol. 63. 1. Sanhedrim, fol. 99. 1.((c) T. Bava Bathra, fol. 12. 1.((d) Abarbinel in Dan. fol. 63. 4. " Source: Ibid.
Matt. 11:13 is a time marker, a time text; and defines that generation in which Christ was manifested (1 Pet. 1:20; Heb. 1:1-3) as the generation that saw the fulfillment of all the OT prophets and of all the old covenant law. Christ fulfilled them all. He did not leave anything unfinished.
That generation of the first century A.D. was that generation that saw Christ walk on this earth, that saw Him crucified, that saw Him ascend into heaven. Christ did not fail in any of the prophesies.
All of the apostles continued to prophesy of the last and final event, namely the destruction of Jerusalem and the temple, at which time His spiritual kingdom, the "promised land" (2 Pet. 3:13) was fully established.
The beloved apostle John was given the last prophesy of that destruction and told he would prophesy again (Rev. 10:11) before many peoples. The word "again" means that the apostle John had already spent much of his time prophesying during the 40 year preaching of the gospel after the crucifixion.
The latter days were finished when the temple was destroyed in A.D. 70, at which time the law was completely fulfilled. That was the end of the latter days, and the end of the prophesies as Gabriel foretold Daniel that his holy people would be scattered (Dan. 12:7)
We are not living in the latter, or last days. That is why all prophesy is now sealed, and has been sealed since A.D. 70.
See the evidences from the scriptures that I have presented at my blog https://shreddingtheveil.org. The series "It's Not The End of The World: Parts I - X" begin at the bottom margin and lay out the sequence.
John the Immersor (baptist) was not the last prophet; the beloved apostle John was the last prophet.