I think this is a good passage for those of us, myself included, who may run with a traditionalist crowd that is more reactionary than some to the changing of disciplines in the Church. Christ, and prophets before him, were legitimate authorities (Abraham, Moses, Elijah) so they had every right and duty to look at the apodictic (principles) which remain constant and then reform their practice (casuistic law) to ensure their fulfillment in a new era. This of course can be taken too far but we would do well to recognize that there is a legitimate authority on earth which has the ability and duty to do this for us now.
Within the Torah itself, and subsequently in the dialog between the Law and the Prophets we already see the contrast between changeable casuistic law, [PreChrist: No Pork. Nowadays: No meat on Fridays during Lent. Sabbath on Saturday vs. Sabbath on Sunday] which shapes the social structure of a given time, and the essential principles [Ten Commandments, Torah] of the divine law itself, in terms of which practical norms constantly have to be measured, developed, and corrected.
Jesus does nothing new or unprecedented when he contrasts the practical, casuistic norms developed in the Torah with the pure will of God ... in his capacity as the Chosen Prophet who sees God face-to-face.
Just a thought.