Try to think of a parallel ...
Since the advent of email, and later, text messaging, people's writing skills have deteriorated. But has it really "deteriorated" or merely "changed"? The language is usually less flowery but we usually get to the point much faster with email and texting. Is that bad?
Since the common adoption of GPS navigators, most drivers' map reading and navigation skills have atrophied, with the younger generation never learn to read a road atlas; but more people are now visiting more obscure places and drive more on lesser known roads. Is that bad?
Now coming to "critical thinking." Why do we want people to think critically? Why do we want our kids and students to think critically? Is "critical thinking" an end by itself or are we trying to achieve certain personal or societal benefits through critical thinking? If the end is some other things and "critical thinking" is merely a means to achieve that end, what if AI can get us to the end faster?

