I think it’s fine to frankly discuss the failings of our Founding Fathers. They were great but weren’t perfect.
The slavery issue was one big way in which they failed to live up to the American Revolution’s ideals of freedom and political equality for all. Women had to wait until 1920 for the right to vote. Natives continued to be discriminated and warred against, and in effect victims of genocide.
That said, the Founding Generation was quite “progressive” for their times. No nation had ever successfully rebelled against a colonial power before, and for examples of democracy in practice, you would have had to have gone pretty much all the way back to Athens.
The American Revolution has directly inspired freedom movements ever since, including the abolitionist movement.
So I think we should grade the likes of Washington, Jefferson, etc. on a curve to an extent.