What’s ignorant about this assertion? The issue here is the discretionary power given to U.S. Presidents by the constitution and the weakness of the other two branches compared to the executive in practice. It’s unclear what that has to do with kings.

Shouldn’t the protests be called “No Presidents” then? US presidents exercise more power than any king ever has.

It’s kind of dumb to call your protest “No Kings” when you’re protesting an elected president.