There is much more to the story than just this parable, and I would encourage you to go and read the rest of Judges, chapter 9 (and on…). Ultimately, the people get what they ask for: an illegitimate king. Also, Jotham’s prediction certainly comes true—there is fire between Abimelech and the people of Shechem, which brings about Abimelech’s downfall. But this is hardly the end of the story. The people keep on asking for a king until God finally grants them to have a human king. And what a mess of people they were. Even the good ones, though they are few, have their low points. This is what happens when we chase after the ways of this world rather than chasing after the things of God, and that point does not just apply to our political leaders, but to all aspects of life.
Friends, chase after the things of God and seek to grow holy. Learn to resist sin and to glorify God in both your public and private lives. Love him in all you do. Love his word—study it, pray it, sing it, and memorize it—and seek his face in prayer. If you do these things, you will stay clear of the seduction of the world. You will keep yourself out from under the choking bramble of sin—not by your strength, but by the strength of the one who dwells in you and is reflected in you more and more clearly as you grow in faith.