"When its twigs are dry, they are broken off and women come and make fires with them. For this is a people without understanding; so their Maker has no compassion on them, and their Creator shows them no favor." NIV translation
When the leaves are stripped off of a tree, it will die and that is what we have pictured here.
In the last part we saw the desperation of people grabbing onto religion like a cow eating leaves from a tree trying to survive in the desert. This tree is a contrast to the one described earlier that took root and produced fruit (verse 6). That tree was rooted in the finished work of Jesus Christ while this tree is religion that is rooted in the efforts of men.
As we see here, those who trust in a religion (work of their hands) instead of Christ will die and be consumed by fire. This speaks of the final judgment of Israel and we see that this judgment is for those that cling to their religion and reject Jesus Christ.
Isaiah sees that those who reject Jesus will not be shown mercy or kindness. This is a reminder that there is only one way to be saved and that is through faith in the finished work of Jesus Christ.
Even now, there is a large effort underway to rebuild the temple in Jerusalem and to begin again the sacrifices and offerings that ceased with the destruction of the temple in 70 A.D. These efforts to restore the religious system are a testament to the fact that the people are a "people without understanding" of the Scriptures that they have received. All of the Torah, the Prophets, and the writings point to the fact that a Messiah was to come but these people do not accept Him. In rejecting Jesus, they reject the One that sent Him which is God in heaven. When a people reject God, they are left to judgment without mercy or kindness.
There are those that spread a false hope that just getting the Jewish people to Israel will make them safe and bring them back to God. This is a lie and an abomination as it is only through faith in Jesus the Messiah that anyone can enter this new shining city of God.