There are a few acceptable ways to interpret this, but it is not acceptable to say that Jesus was wrong. That is a heretical statement - Jesus was omniscient (fully God) during His earthly life. I would not attend a Mass celebrated by this priest as he may be excommunicated.
Now, the truth is that this is a dual prophecy. Here is what the disciples asked our Lord:
“Tell us,” they said, “when will this happen, and what will be the sign of your coming and of the end of the age?”
And so Jesus answered them: He told them when the Temple would be destroyed, and when the Second Coming would take place. On the first level, the answer is obvious: “this generation” - Jesus’ immediate audience - did not pass away before God judged Israel, using the Roman Empire, which destroyed the Temple in 70AD. On the second level, we’ll need to look at more of what Jesus said:
“Now learn this lesson from the fig tree: As soon as its twigs get tender and its leaves come out, you know that summer is near. Even so, when you see all these things, you know that it is near, right at the door. I tell you the truth, this generation will certainly not pass away until all these things have happened. Heaven and earth will pass away, but my words will never pass away.”
The lesson from the fig tree is this: Jesus had just cursed the fig tree and it shriveled up and died (Matt. 21:18). This signified God’s judgment on Israel, which “died” in 70AD. So, when you see the fig tree come back to life, know that “this generation will certainly not pass away until all these things have happened.”