There is no indication that this message is exclusively for Jews. If what your saying is true then no more Jews could come to Christ after next year? There are countless Jews who came to Christ in the last 2000 years. No the message is that God is kind and patient towards us but if we persistently choose not to repent after receiving grace then He will eventually give us over to a depraved mind.
First, you have to accept that Jesus first coming was only for Israel (Matthew 15:24, Romans 15:8)
The gospel of the kingdom was only meant for Israel (Matthew 10:5).
Once you realized that, then
second, you must be aware that
Fig tree, vineyard and olive are always symbols in scripture
referring to Israel and the Jews.
Some examples from the OT show that The fig tree is symbolic of Israel itself – It often symbolized the health of the nation both spiritually and physically. Hosea 9:10 says,
“When I found Israel, it was like finding grapes in the desert; when I saw your ancestors, it was like seeing the early fruit on the fig tree.”
Later, the Bible tells us of the glorious time when
“Judah and Israel lived in safety, every man under his vine and his fig tree, from Dan even to Beersheba, all the days of Solomon.” (1 Kings 4:25)
The fig tree is a picture of Israel. In Jeremiah 24, we read about the prophet’s vision of two baskets of figs. Every person in Israel was symbolized by those figs. This means that the whole nation is one or several fig trees from which come the figs, the individual Israelites.
Elsewhere in the OT, when God was displeased with His people because of their unfaithfulness, He would make it known by referring to the lack of fruit on a fig tree. We have an example of this in Jeremiah 8:13. "I will surely consume them," says the Lord. "No grapes shall be on the vine, nor figs on the fig tree, and the leaf shall fade; and the things I have given them shall pass away from them."
Here again, Israel as a nation is symbolized by a fig tree.
Once you are able to accept my above 2 points, then it will be easier for you to understand my conclusion, that the parable of the barren fig tree in Luke 13:6-9 can only refer to Israel and Jews.
To address your final point, after Israel the nation has fallen in the eyes of God, as stated in Romans 11:11, everyone, Jew and gentile, are considered uncircumcised in the eyes of God and can now enter the Body of Christ thru Paul's gospel of grace.
That is where Jews for the last 2000 years, as you have stated, have been entering the Body of Christ, with us gentiles.