That is a foolish myth spread by Hoppe and other Rockwellites. You could certainly make a case that there was greater liberty and smaller government before the French Revolution than after it. Or that it was easier to evade rulers in pre-modern societies.
But the oriental despotisms of the world prove beyond question that absolute monarchy is far from "the most libertarian form of government." Or, if it is, that says very little for libertarianism.
And while feudalism allowed much freedom from the state and its ruler, it subordinated individuals to other lords to a great extent. Those who take this view ignore what it would have been like to have been bound to the land, and exaggerate the difference between taxes and feudal dues.