"...it still requires a great deal of effort for us today to grasp Kant's philosophy in its essential import and to liberate it from the misinterpretations of its contemporaries and advocates."

(Martin Heidegger, Nietzsche vol. 2: Eternal Recurrence of the Same)

Indeed, it is most difficult to liberate from its fiercest contemporary and advocate--in other words, it is most difficult to liberate from Kant himself.