Granted the cancelling of great people like John A. MacDonald (without whom we would have been annexed by the Americans, and certainly would never have become Canada as it presently stands) and others, it's worth looking to George F. Will's remarks on presentism in The Conservative Sensibility (2019).
[Presentism is] the practice of judging the past by the standards of the present. This amalgam of ignorance and arrogance invariably leads the complacent people doing the judging to flatter themselves as much more discerning, sensitive, and generally better than say, George Washington, who did not free his slaves, or Abraham Lincoln, who never allied himself with abolitionists. It is peculiar. Practitioners of identity politics insist that their contemporaries be understood, and empathized with, entirely as situated products of their race, ethnicity, gender, or class. But these practitioners cannot make the imaginative leap of placing themselves in the historical situations of earlier generations that grappled, as all generations do, with reconciling universal moral principles with the inertia of institutions and mores in the society they had inherited from earlier generations. Presentism is an intellectual failure to which progressives are especially susceptible because, believing in the upward unfolding of history, they are confident that they are the pinnacle—so far—of human understanding. But by validating each generation’s vanity, presentism stunts the historical imagination that enables us to take pleasure as well as instruction from our place in continuum with our distinguished predecessors. People who flatter themselves by engaging in presentism should remember that they are tomorrow’s past. By condescending to the past, they make themselves hostages to the condescension of the future.
Over a century ago, G.K. Chesterton similarly identified the problems at the heart of as well as resulting from this "intellectual failure." Like Will, Chesterton called out the arrogance of so-called progressives; those who think Wednesday is better than Tuesday merely because it is a day ahead (“My attitude toward progress has passed from antagonism to boredom. I have long ceased to argue with people who prefer Thursday to Wednesday because it is Thursday.”) More importantly, he underscored the importance of not throwing out the past, those who have passed, or the wisdom from either. He wrote in Orthodoxy (1908):
Tradition means giving a vote to most obscure of all classes, our ancestors. It is the democracy of the dead...Tradition refuses to submit to the small and arrogant oligarchy of those who merely happen to be walking about. All democrats object to men being disqualified by the accident of birth; tradition objects to their being disqualified by the accident of death. Democracy tells us not to neglect a good man’s opinion, even if he is our groom; tradition asks us not to neglect a good man’s opinion, even if he is our father.