The story of every nation on the planet has triumphs and tragedies. The United States is no different.
What matters is whether a nation learns and evolves or if it sinks into corruption and despotism.
The Founding Fathers were the product of their era. They should be judged not by the standards of today but what they did to advance civilization and the cause individual liberty for all people. The Declaration of Independence certainly made the case for individual liberty and self governance in an era where authoritarian rule by hereditary monarchs was the rule. The Constitution institutionalize a republican government which did not end slavery or include women’s suffrage but it did provide a framework which could be expanded to be more inclusive over time. It also institutionalized a rule of law that protected property rights and facilitated the growth of a capitalist economy which allowed the US to become the largest and most prosperous economy in the world.
The great gift of the Founders was creating a representative government that ultimately extended unalienable God given rights to all citizens AND protected the exercise of those rights by citizens pursuing their own destiny. This was a turning point in the advancement of human civilization. That accomplishment cannot be diminished or denigrated by anyone who truly believes in liberty.
Measured by the advancement of liberty over the past 250 years in America, the progressives of today’s left are failures. They reject universal natural rights, granted by God, for privileges given to citizen servants of the state based on arbitrary and ever changing “values” determined by the ruling class.
Instead of inalienable rights, history is about a struggle for power, and part of that power struggle is the fight of the subjugated against subjugation. "Rights" only arise when the subjugation ends, which can usually only be achieved through violent struggle. Sometimes this struggle creates a worse despotism than the one it displaces (French Revolution, Communist Revolutions), sometimes it creates something far greater and enduring (the American Revolution).