We might never defeat terrorism but we can cut out its causes
In his own words, the purpose of that essay was to suggest that "a remarkable consensus concerning the legitimacy of liberal democracy as a system of government had emerged throughout the world over the past few years, as it conquered rival ideologies like hereditary monarchy, fascism, and most recently communism."
He went on to argue in the essay that liberal democracy may constitute the "end point of mankind's ideological evolution" and the "final form of human government." In other words, while other forms of government were characterised by grave defects and irrationalities that led to their eventual collapse, liberal democracy was free from such fundamental internal contradictions. He wasn't arguing that the stable democracies of the world were free from injustice or serious social problems, rather that these problems arose from inadequate application of the principles of liberty and equality on which modern democracy is founded.