Liberalism was an improvement over monarchy for a specific class of merchant. The system has continued success for said class.
Using 1776 seems like a “life begins at conception” argument. The currently constituted system began closer to 1787. Declaration of Independence was issued in 1776. The Articles of Confederation were ratified in 1781. The Constitution was ratified in 1787.
There is not a continuum of political progress. Looking back at historical records, it is easy to create a narrative that political progress, like time, is linear and progressing toward some goal.
Systems without heirarchy continue to be an option. Prefiguring such a system without a monopoly on violence is the tricky bit.