Adams, Harrison, Roosevelt, Kennedy, Bush, Clinton. That spans the entire history of the country, and doesn't leave much room for cycles. I can't think of any period when inherited wealth and connections weren't extremely helpful in a political career.

I'd say that "ossified authoritarian impulses built deep into [the] system" is a global issue, not a uniquely American one.

A better answer is that contemporaneous class systems elsewhere in the world were so rigid, early in American history, that merely not having formal orders of nobility seemed shockingly egalitarian. Two and a half centuries later we're less eager to pat ourselves on the back for somewhat-better-but-only-somewhat levels of equality. But failure to make enough progress is not the same as regression.