Excerpt:

A similar line of argument is attempted by the skeptic Tim Callahan in Bible Prophecy?: Failure or Fulfillment? “Obviously,” Callahan writes, “the gospel had not been preached to the entire world by 70 C.E., even if we interpret the whole world as being nothing more than the Roman Empire.”[1] He makes a mistake by mistranslating the Greek word oikoumenē in Matthew 24:14 as “world.” Some of the confusion on this issue is because of some less than helpful translations found in the King James Bible where the Greek word aiōn (“world” instead of “age: Matt. 24:3) and oikoumenē (“world” instead of “inhabited earth”: Matt. 24:14).

Oikoumenē is a word that illustrates limited geography. The gospel only had to be preached as far as Rome could tax since the same Greek word is used in Luke 2:1. Had the gospel been preached throughout the Roman Empire before that generation passed away? The Apostle Paul tells us that the gospel had been preached “to every creature under heaven” (Col. 1:23). In other places where we read that the gospel was “being proclaimed throughout the whole world” (Rom. 1:8: here the Greek word kosmos is used) and had been “made known to all the nations” (16:26).

Full article: https://americanvision.org/posts/christians-give-up-the-faith-because-of-this/