“Be not moved away from the hope of the gospel, which you have heard and which was preached to every creature which is under heaven” (Col 1:23)
Col 1:23 says that the gospel was preached to every creature under heaven, therefore the command in the New Testament to preach the gospel has been fulfilled
The gospel had to be preached to the Roman world and then the end of the age (Matt 24:3) would happen, that’s what Matt 24:14 is saying. Matt 24:14 is not saying, “the gospel has to be preached to entire planet”
The Greek word “oikoumene” for the word “world” in Matt 24:14 is referring to the Roman world, “oikoumene” is also the word that is used for the word “world” in Rev 12:9, both Matt 24:14 and Rev 12:9 are talking about the Roman world.
Matt 24:14 and Rev 12:9 are not talking about the entire planet
Rev 12:9 And the great dragon [the dragon in Rev 12:3 is Rome] was cast out, that old serpent, called the devil, and satan, which deceiveth the whole world [oikoumene – the Roman world], he was cast out to the earth, and his angels were cast out with him.
Matthew 24:14 And this gospel of the kingdom shall be preached in all the world [oikoumene – the Roman world] for a witness unto all nations; and then shall the end [of the age] come.
The “end” that is spoken of in Matt 24:14 is the “end of the age” that is spoken of in Matt 24:3
The gospel had to be preached to the Roman world as a whole before the end of the age
The Greek word for the word “world” in Matt 24:3 is “aion” or “age”, the word “aion” or “age” is referring to a time period, the word “aion” is not referring to the entire planet
Matthew 24:3 And as the Messiah sat upon the mount of Olives, the disciples came unto him privately, saying, Tell us, when shall these things be? and what shall be the sign of thy coming, and of the end of the world [aion – age]?
The age that is spoken of in Matt 24:3 is the age of the law, the Mosaic age.
The end of the age happened when the temple was destroyed during the destruction of Jerusalem in 70AD, therefore everything in Matt 24, Mark 13 and Luke 21:5-33 has already happened.