It’s definitely invalid because the generation Jesus was referring to was the one He was talking to.
There would be no reason to give the parable - to that generation.
Matthew 24 is addressing two groups. (1) Jews (them who arre not Christians), Israel, in the end times when Jesus returns to this earth. (2) Christians in the end times, to be ascertain that they are living in the end times, via the parable of the fig tree, and instructions to watch because we don't know the hour of His Coming in the rapture event to avoid going through the great tribulation.
(1) Jesus in Matthew 24:15-31 is addressing the end times generation of Jews, Israel, who will end up going through the great tribulation. And what them living in Judea must do to survive it.
(2) Differently, in Matthew 24:32-51, Jesus is addressing Christians, the end times generation who are looking for His coming,
to know the season by the parable of the fig tree. No-one knows the hour. Christians consider Jesus to be our Lord. Jews (Judaism) do not.
Matthew 24:
42 Watch therefore: for ye know not what hour your Lord doth come.
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1948 Israel a nation again in the land in one day. Isaiah 66:7-8
1967 Jerusalem in the hands of the Jews. Jerusalem a cup of trembling to the nations. Zechariah 12:2
The Gog/Magog nations in place - Gog/Magog to happen in the 1967 generation.