This is most noticeable in fields like medicine and especially psychology, where anyone disagreeing with whatever the consensus is at the moment is considered an anti-scientific flat-earther, whereas the fact that this consensus itself nearly reverses every couple decades is rarely brought up.
Which vicennial cycles of academic consensus have you found most noticeable?
Well, the standard example is nutrition advice. Other reasonably well-known examples include whether post-menopausal women should take estrogen supplements, and how dangerous marijuana is. An example with a longer period is the whole issue with eugenics.
Here's another installment of rationality quotes. The usual rules apply: