The essential Neocon failure is the failure to recognize reality, and such people can’t be left in charge of U.S. foreign policy. From Ron Unz at unz.com:

Husband and Wife: Bush Neocon Robert Kagan and Obama/Biden Neocon Victoria Nuland
Last week I discussed the ironic role that America’s dominant Neocons may have played in shaping recent world events, perhaps inadvertently producing a beneficial outcome exactly contrary to their aggressive intent.
Over the last decade, prominent political scientists such as Graham Allison of Harvard and John Mearsheimer of the University of Chicago had argued that a centuries-long pattern suggested that the world was locked into a “Thucydides Trap,” the likelihood of a looming clash between the reigning global power of America and the rising global power of China. This political and potentially military conflict had nothing to do with the ideological or social characteristics of those two enormous countries nor their leadership, but was simply the inevitable consequence of China’s size and growing power, which threatened to displace America from its position of world dominance. The term referred to the analogous rivalry between Athens and Sparta that had unleashed the long Peloponnesian War, devastating Classical Greece.
Meanwhile, on totally different grounds the ideologically-driven foreign policy of America’s dominant Neocons also threatened global warfare against all countries that refused to accept American hegemony, with Russia and Iran being the leading targets of their intense hostility. During the Obama Administration, these individuals had orchestrated a 2014 coup that overthrew Ukraine’s democratically-elected pro-Russian government. Seven years of military buildup and anti-Russian provocations had eventually led to the outbreak of the Ukraine war in early 2022, with the first year of the fighting having already cost many tens of thousands of lives while raising the risk of World War III.