The verse where he tells his disciples that “this generation will not pass away until all these things take place” would seem to be at odds with that. A lot of Biblical canon is at odds with itself, the Bible doesn't have a singular coherent narrative. I'm just suggesting an interpretation which seems more likely than not.
Just look at history - almost every generation of Christians have believed the end times would occur within their lifetimes, or at least the near future. Why would only the first generation accept that, no, it would be some thousands of thousands of years in the future? That isn't the way these things tend to work.