I tell you the truth, this generation will certainly not pass away until all these things have happened Matthew 24:34
It is the same word used at Matthew 17:16-18 where is is very clear to me that he is addressing his own people.
"O unbelieving and perverse generation," Jesus replied, "how long shall I stay with you? How long shall I put up with you? Bring the boy here to me."
He does not need to "put up" with the unbelieving nations for the simple reason being they are not with him.
"This" generation means Jews. The creators of the NT knew it would take forever to convert the Jews to their new religion. In the meantime they collect mucho bucks spreading their fear beliefs that Jesus is coming back any minute knowing ALL Jews will not be converted.