"'But these people have stubborn and rebellious hearts; they have turned aside and gone away. They do not say to themselves, "Let us fear the Lord our God, who gives autumn and spring rains, who assures us of the regular weeks of harvest."'" NIV translation
Even though the people had known that God was the creator and was in control of all things, they still rebelled. This reminds us that it is not merely a "head knowledge" of the things of God that is required to be saved. A change of heart is required and that change of heart is commonly called repentance.
"'Your wrongdoings have kept these away; your sins have deprived you of good.'" NIV translation
God makes it clear that the judgment of famine is due to their rejection of Him. God is not only the Creator but also the Sustainer of all things. When they rejected Him, then, God was no longer under obligation to provide for them. This is another example of how God's judgment was justified.
Even as Christians, our sins can rob us of the good things that God has in store for us. We are guaranteed salvation but we are also given freedom to make choices every day. Those choices can either lead us to the good (blessings) that God has put in place for us or they can lead us in our own direction and the struggle to provide for ourselves.
"'Among my people are the wicked who lie in wait like men who snare birds and like those who set traps to catch people. Like cages full of birds, their houses are full of deceit;'" NIV translation
God compares the actions of His people to those who trap birds and put them in cages. At first glance, we would not think too much of this as we are familiar with keeping birds in cages as pets. It was not like that in Jeremiah's time as birds were caught for food or for sacrifices but not for pets. Although we are free to do so, it is sad to think that birds who God created to fly freely through the sky are put in a cage where they mostly just sit on a perch.
Imagine how the bird that is used to soaring in the sky feels when all it can do is sit on a perch. In the same way, people can get caught up in their sin where they cannot soar like God desires for us. This is the same type of frustration. We can escape that cage through Jesus Christ and be free to soar again!